Method for reducing exhaust carbon dioxide

ABSTRACT

A method for effectively absorbing and removing CO 2  in an exhaust gas generated during an industrial process for reducing the amount of CO 2  that is exhausted into the atmosphere. The exhaust gas containing CO 2  is blown into an agglomerate of solid particles containing CaO and/or Ca(OH) 2  so that the CO 2  is in contact with the agglomerate for fixing the CO 2  in the exhaust gas as CaCO 3 , thereby reducing the CO 2  concentration in the exhaust gas. Preferably, the solid particles contain water, and more preferably, the solid particles contain surface adhesive water.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No.09/844,533 filed on Apr. 27, 2001, which is a continuation applicationof International application No. PCT/JP99/05972(not published inEnglish), filed on 28 Oct. 1999, the entire contents of which areincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a method for reducing CO₂ concentrationin exhaust gas generated in an industrial process and others, andreducing the amount of exhausting CO₂ in an atmospheric air. Further,the present invention relates to a water immersion block for seaweed andalgae planting places, fish gathering rocky places or riverbeds, and amethod for making the same. Herein, the above mentioned “seaweed andalgae planting places” designate groups or communities of marine algae(algae, seaweed and the like) growing in the sea bottom.

BACKGROUND OF THE INVENTION

Recently, from the viewpoint of preventing world warming, it has beendemanded to reduce the amount of generated CO₂ on a global scale. At thecongress of the world warming prevention which took place at Kyoto inDecember 1997, a protocol for the reduction of the exhaust gas wasadopted. This protocol established a reduction target in 2010, aiming atreducing at least 5% of a standard with respect of 1990 of the exhaustamounts of greenhouse effect gases (CO₂, CH₄, N₂O and others) of alladvanced countries. In accordance with the protocol, Japan has beenassigned a duty of lowering 6% of the amount of issuing exhaust gases.

CO₂ accounts for 64% of the contribution degree per the greenhouseeffect gas with respect to world warming, and is mainly exhausted byusing fossil fuel. In Japan, 95% of the greenhouse effect gas generatedby social or economical activities is CO₂, and more than 90% thereof isaccompanied with use of energy. Accordingly, a measure for preventingthe world from warming will be to chiefly control CO₂ exhausted inconjunction with the use of energy.

With respect to the control of exhausting CO₂ accompanied with the useof energy, for example, the iron and steel business world which accountsfor about 11% of the final energy consumption of Japan, projects aself-imposed behavior plan toward 2010, and proclaims in this plan a 10%reduction, in comparison with 1990 of the energy consumption in theproduction process in 2010. Further, as an actual measure thereto otherthan energy reduction, included are the blowing of waste plastics asreducing agents into blast furnaces, usage of non-used energy inneighboring areas, or contribution to energy saving by making productsor by-products.

However, in the present high degree industrialized society, there is perse a limit in the control of using energy which is related to thecutting of the exhaust of CO₂, and it is not always easy to accomplish atarget of cutting CO₂ exhaust only with the control of the amount ofenergy used.

Accordingly for accomplishing the target of cutting CO₂ exhaust, it isconsidered to be necessary to take such a measure from both sides ofcutting the CO₂ generated amount, as well as removing CO₂ from thegenerated gas (exhaust gas). However, an effective method which removesCO₂ from the exhaust gas on an industrial scale is not yetconventionally known.

As a part of usefully using slag generated in the iron and steel makingprocess, it has been tried to make use of the slag as a seawaterimmersion block for algae planting places or fish gathering rockyplaces.

As main embodiments of utilizing slag as such materials, there is amethod of utilizing massive slag for algae planting places as it is, andanother method of utilizing slag as agglomerates for fish gatheringrocky places. However these methods are involved with problems asdiscussed herein.

In the former method, Ca content contained in slag is dissolved into thesea to probably heighten the pH in the neighboring seawater. Theobtained massive slag in the iron-steel making process is suited as ablock for such as algae planting places due to surface properties incomparison with concrete products. However, as a block for the algaeplanting places, the massive slag has functions (adhering property ofsea algae or rearing property) only of a similar degree to a naturalblock, and does not have a special function of accelerating the growingof sea algae.

The slag generated in the iron-steel making process contains much ironcontent such as metals (grain iron), and ordinarily it is broken todesired sizes for recovering the iron content in the slag for recycle inthe iron-steel making process. Slag for algae planting placesnecessitates sizes of a certain degree, and slag broken for recoveringthe metal is scarcely used. If use is made of the massive slag as ablock for algae planting places, the recovery of the metal useful asiron and steel sources can hardly be practiced.

In contrast, if massive slag containing much metal is immersed into thesea as it is for use as a block in algae planting places, the ironcontent in the slag is oxidized, depending on sea areas, to cause ashortage of oxygen in the seawater, and further by dissolution of theiron content; the iron content might be excessively supplied in the seawater. For avoiding such problems, the metal in the slag should beperfectly removed. Since the slag content and the metal generally existin a mixture as if entwined, the slag must be more finely pulverizedthan the case of the above mentioned metal recovery in order tocompletely remove the metal. Such finely pulverized slag cannot be usedas materials to be immersed in the sea water for the algae plantingplaces.

On the other hand, the latter method uses slag as an agglomerate of aconcrete made pre-cast body, and so there seldom occurs a problem of thecase that the massive slag is immersed in the sea as it is. Howevermaterials available by this method are concrete products whose surfacesare composed of cement mortar, and which therefore cannot exhibit eventhe properties of massive slag (for example, uneven surface property)which are expected to display performance per se as for algae plantingplaces.

Recently, there has arisen a tendency towards maintenance andimprovement of natural circumstances of rivers including livingcircumstances of creatures such as fishes or shells, and as a part ofthe tendency, for example, it has been tried to repair riverbeds to besuited to water living creatures (fishes, shells, water insects andothers) or water plants (algae, water grass and others) to inhabit andlive. In the rivers, creatures' living and resting spaces calledbiotopes are created with blocks and, accordingly, much uneven riverbedsmade by blocks are better for water living creatures. Relatively largespaces among immersed or half-immersed massive blocks on the riverbedsor small spaces among small blocks laid thereon are important livingspaces (biotopes) for water living creatures. Blocks on the riverbedsare also places for water plants to live, and for rearing water plants.Blocks are therefore important.

For repairing riverbeds as a part of maintenance or improvement of thenatural circumstances of rivers, the sinking or laying of blocks inappropriate forms (for example, placing of large massive blocks, sinkingor laying of middle massive or small blocks on the riverbeds) may be auseful means for arranging the circumstances for fish to live orinhabit. For repairing riverbeds, enormous amount of blocks arerequired. It probably causes destruction of nature to supply naturalblocks from other places, and since natural blocks are not cheap, theconstruction cost is increased.

For usefully using slag generated in the iron and steel making process,it has been tried to utilize slag as sea water immersion blocks for fishgathering rocky places. Concerning blocks for sinking in rivers, slaggenerated in the iron and steel-making process should be considered.

As discussed hereinabove, with respect of main embodiments for utilizingslag to be immersed in rivers, there is considered a method of using theslag as it is as an immersion block and another method of using the slagas concrete pre-cast agglomerates.

However these methods have problems as discussed hereinabove.

In the former method, the Ca content in the slag is dissolved into thewater to probably heighten the pH in the river water. Since the slaggenerated in the iron and steel making process contains much metal(grain iron), if massive slag is immersed in the water as it is, grainiron is oxidized, and depending on water ranges, a shortage in oxygenmight occur in neighboring rivers. For avoiding such problems, the metalin the slag should be completely removed. Since the slag content and themetal generally exist in a mixture as if entwined, the slag must be morefinely pulverized than in the case of the above mentioned metal recoveryin order to completely remove the metal. Such finely pulverized slagcannot be used as materials to be immersed in the sea water for algaeplanting places.

On the other hand, as in the latter method, if the slag is used as anagglomerate of a concrete made pre-cast body, since the base is made ofconcrete, the properties of the massive slag (for example, unevensurface property) which are expected to display performance as animmersion block in the rivers cannot be displayed. The concrete has ahigh pH (ordinarily, about a pH of 12 to 12.5), so that it increases thepH in the neighboring river water or delays growth of algae.

It has recently been recognized to prepare fish ways for fishes to moveto upstream or downstream or to go up in dams or barrages, and repairstherefore have been carried out. The fish way is provided with awaterway (usually, having a width of about 2 to 5 m) for forming flowsfor fish to move in parts of the dam or barrage, and known are slantpaths or stepwise paths. Conventionally ordinary fish ways are made bycutting parts of the dam or barrage in the water path encircled with theconcrete.

Thus, the conventional fish way has no obstacle for fish to move as longas no problems exist in water flowing speed, water bottom obliquity orsteps. However, since the concrete-made fish way has a smooth bottom, itis difficult for water living creatures such as algae to live, and thereare problems for water living plants (for example, crusts or waterliving insects) relating to moving because of the catching with theirclaws on the riverbed (surface projections as a block for water livingplants). For these problems, there is a method of structuring the fishway with a foam concrete to make fine indentations on the bottom of thefish way, however the construction cost is high with lesspracticability. In either way, the concrete has a high pH, which is notpreferable for water living creatures moving on the riverbed.

Algae planting places are for breeding sea living plants and creaturesin coastal and sea areas, and are indispensable as living places foruseful fish and shellfish, rearing marine algae, laying eggs of fish andshellfish, breeding fry and small fish, or baiting. In addition,recently, nitrogen or phosphorus in the seawater are taken in by marinealgae or other living creatures through the food cycle or chain in thealgae planting places, otherwise suspension materials subside in thealgae planting places. Thus, a water purifying action has been noticed.

However, nowadays, the algae planting places continue to rapidly fade ordecline by influences of reclaiming coasts or corruption of theseawater. In particular, recently, in many coastal or sea areas, a bigproblem of so-called “shore burn” phenomena occurs. It has thereforebeen demanded to establish an algae place creation act for recoveringalgae planting places.

Algae creating methods conventionally carried out are roughly divided inthe following two ways.

(1) At places where algae planting places are desired, bases for rearingmarine algae (mainly, natural blocks or concrete blocks) are laid, andseeds and saplings of marine algae or mother algae are transplanted, andmanaged for rearing them as required.

(2) Places environmentally easy to become algae living places, that is,such places suitable for creating the algae places in view ofcircumstances as water depth, water quality or ocean current, which arewithin reach of spores of marine algae from existing algae places, areselected, and the bases are laid there. Algae places are thus createdwhich are maintenance free (transplanting or rearing managing are notbasically done).

Of these methods, the method (1) is advantageous in wide selectingranges for creating the algae places, however, basically all of thecreations are artificial, and it is necessary to fully managetaking-roots or rearing of transplanted seeds and saplings, for which alot of time and tremendous cost are taken. This method is absolutelyunsuited to large scale creations of algae places.

On the other hand, as the method (2) creates algae places which aremaintenance free, other than laying the bases, it is advantageous inthat it takes less time and cost, in comparison with the method (1).However, this method is short with respect of general purpose usesbecause of limited places to become algae places. According to a certainreport for creating an algae place by the method (2), at a proper periodin a place which does not naturally become an algae place, it ispreferable to select a place within 100 m from an existing algae place,taking into consideration the reach of spores or seeds from existingalgae places. Accordingly, it is assumed that this method is difficultto create algae places at places where circumferentially whole algaeplaces have been faded by shore burn.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide a method thateffectively absorbs and removes CO₂ in an exhaust gas generated in anindustrial process for reducing an amount of exhausting CO₂ into theatmospheric air.

The inventors made detailed investigations on materials of absorbing CO₂and a method of using the same in order to find a method whicheffectively absorbs and removes CO₂ in the exhaust gas on an industrialscale. As a result, they found that as the CO₂ absorbing material,optimum was an agglomerate of solid particles containing CaO such asslag or concrete. The inventors also found that by blowing exhaust gascontaining CO₂ in an agglomerate of the solid particles to be in contactwith the exhaust gas, and especially preferably by blowing the exhaustgas, under the condition that the gas dissolves into the suitable amountof water content and the successive reaction (more preferably, surfaceadhesive water of the solid particles) to contact with the exhaust gas,it was possible to fix CO₂ in the exhaust gas as CaCO₃ in the solidparticles and effectively absorb and remove CO₂.

The present invention has been realized on the above-mentioned findingsand is described as follows.

[1] A method for reducing an exhaust carbon dioxide comprising the stepsof:

-   -   preparing agglomerates of solid particles containing at least        one compound selected from the group consisting of CaO and        Ca(OH)₂;    -   contacting an exhaust gas containing CO₂ with the agglomerates        of the solid particles in a reaction chamber, the solid        particles having a film of adhesive water on a surface of the        solid particles;    -   fixing CO₂ in the exhaust gas as CaCO₃ to reduce CO₂ in the        exhaust gas.

[2] The method according to [1], wherein the agglomerates of the solidparticles are obtained by pulverizing materials containing CaO and/orCa(OH)₂ into grain and/or rough grain.

[3] The method according to [1] or [2], wherein the step of contactingthe exhaust gas comprises contacting by blowing the exhaust gas into theagglomerates of the solid particles.

[4] The method according to [3], wherein the exhaust gas containing CO₂is blown into the agglomerates of the solid particles from onedirection.

[5] The method according to [1]-[4], wherein the water content in theagglomerates of the solid particles is from 3% to 20%.

[6] The method according to [1]-[5], wherein a grain size Of the solidparticles is substantially 5 mm or less.

[7] The method according to [1]-[6], wherein the temperature of theexhaust gas to be introduced into the reaction chamber is at the boilingpoint of water or lower within the reaction chamber.

[8] The method according to [1]-[7], wherein the temperature in thereaction chamber is at the boiling point of water or lower.

[9] The method according to [1]-[8], wherein the temperature of theagglomerates of the solid particles is the boiling point of water orlower within the reaction chamber.

[10] The method according to [1]-[9], wherein the step of contacting theexhaust gas containing CO₂ with the agglomerates of the solid particlescomprises contacting a pressurized exhaust gas with the agglomerates ofthe solid particles.

[11] The method according to [1]-[10], further comprising the step ofsaturating H₂O in the exhaust gas, prior to contacting the exhaust gaswith the agglomerates of the solid particles.

[12] The method according to [1]-[11], wherein the agglomerates of thesolid particles are at least one selected from the group consisting of aslag generated in an iron-steel making process and a concrete.

[13] The method according to [1]-[11], wherein the solid particles ofthe agglomerates are at least one selected from the group consisting ofa slag generated in an iron-steel making process and a concrete.

[14] The method according to [1]-[11], wherein the agglomerates of thesolid particles are at least one selected from the group consisting of aslag generated in an iron-steel making process, a concrete, a mortar, aglass, an alumna cement, and a CaO containing refractory.

In the invention, CaO and Ca(OH)₂ contained in the solid particles aresufficient with those contained as at least one part of the compositionof the solid particles, and accordingly, concerning other than CaO andCa(OH)₂ as mineral, there are also included those existing in the solidparticles as one part of the composition such as 2CaO.SiO₂, 3CaO.SiO₂ orglass.

It is a second object of the present invention to provide a waterimmersion block. The immersion block is excellent for rearing algae andbreeding fish and shellfish without heightening the pH in seawater orriver water. The present invention also provides a method of making thesame, and a further method of building an algae planting place using awater immersion block.

For accomplishing the above-mentioned object, the present inventionprovides a water immersion block for immersion in water made by a methodcomprising the steps of:

-   -   preparing a mixture comprising grain like slag generated in an        iron-steel making process; and    -   introducing carbonation to said mixture to generate a carbonized        substance, and making the mixture massive with a binder of the        generated carbonized substance.

Blocks made by this method for sinking in the water may be used inseawater or in the fresh water of rivers.

The grain like slag may be at least one selected from the groupconsisting of grain like slag, rough grain like slag and small massiveslag, otherwise the slag may be grain like or rough grain like slaghaving been passed through a metal removing treatment.

Further, the invention provides a method of making immersion blocks forimmersion in water comprising the steps of:

-   -   preparing a mixture composed of grain like slag generated in the        iron-steel making process;    -   forming layers filled up with said mixture; and    -   causing a carbonation reaction in the mixture in a packed bed by        using carbon dioxide so as to make the mixture massive.

The step of forming the packed bed may depend on forming mountains bypiling the mixture.

The invention provides a method of building algae planting placescomprising the steps of:

-   -   temporarily sinking weighty materials on existing algae planting        places, and planting to rear marine algae on the surface of the        weighty materials;    -   recovering the weighty materials and moving them as seeding        materials to places for planting algae; and    -   arranging other materials for planting marine algae around the        seeding materials and increasing the marine algae on the seeding        material onto other seeding materials.

The above mentioned steps are only one example, and may not necessarilyfollow the above method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing assuming a mechanism that CO₂ in theexhaust gas is absorbed and fixed on the surface of the solid particlecontaining CaO.

FIG. 2 is a schematic drawing showing one embodiment of the inventivemethod using a fluidized bed of the agglomerate of solid particles.

FIG. 3 is a schematic drawing showing one embodiment of the inventivemethod using a rotary kiln.

FIG. 4 is a schematic drawing showing one embodiment of the inventivemethod, wherein CO₂ containing gas is blown from one direction into thepacked bed of the agglomerate of solid particles.

FIG. 5 is a schematic drawing showing a method according to the presentinvention of making a seawater immersion block.

FIG. 6 is a schematic drawing showing an actual example of the method ofFIG. 5.

FIG. 7 is a schematic drawing showing another method according to thepresent invention of making a seawater immersion block.

FIG. 8 is a schematic drawing showing an actual example of the method ofFIG. 7.

FIGS. 9A, 9B and 9C are schematic drawings showing structural exampleswhere river water immersion blocks are laid or built on artificialstructural parts or artificial riverbeds, such as a fish way.

FIG. 10 is a schematic drawing showing a method of making a river waterimmersion block according to the present invention.

FIG. 11 is a schematic drawing showing an actual example of a method ofmaking a river water immersion block according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment for carrying out the present invention is as follows.Namely, the first embodiment uses, as a CO₂ absorbing material, theagglomerate of solid particles containing CaO and/or Ca(OH)₂ such asslag or concrete, CO₂ in the exhaust gas is absorbed and removed bymeans of contacting the CO₂ containing exhaust gas with the agglomerateof solid particles for fixing CO₂ in the exhaust gas as CaCO₃ in thesolid particles by the following reaction. In this embodiment, as amethod for contacting the exhaust gas, it is preferable to blow theexhaust gas into the agglomerate of solid particles, and more preferableto blow the exhaust gas from one direction. The exhaust gas can be blownfrom an upper side, from a lateral side and from a lower side. However,blowing from the lower side is easier to handle this method.CaO (solid particles)+CO₂ (exhaust gas )→CaCO₃ (solid particles)

Conventionally, the agglomerate of solid particles containing CaO asslag is hardened by a carbonation reaction with CO₂, and employs thehardened material for architectural or civil engineering. The presentinvention utilizes the carbonation reaction between CO₂ and theagglomerate of CaO containing solid particles for reducing CO₂ in theexhaust gas, which is quite a novel concept in contrast to the priorart. The method of the present invention has been established especiallyfor reducing carbon dioxide.

In the first embodiment, the agglomerates of the solid particlescontaining CaO are used. The agglomerates of the solid particles arecontacted with the exhaust gas containing CO₂. CO₂ in the exhaust gas isfixed as CaCO₃ with the solid particles. In the first embodiment, it ispreferable to contact the exhaust gas with the solid particles throughan appropriate amount of the water content contained in the solidparticles. It is more preferable to contact the exhaust gas with thesolid particles under the condition where the water is adhered to thesurface of the solid particles (water film). The above-mentionedcontacting methods make it possible to effectively heighten theabsorbing rate of CO₂ in the exhaust gas by the solid particles.Therefore, in the first embodiment, it is preferable that the main solidparticle comprising the agglomerate of the solid particle containswater, and it is more preferable to have surface adhesive water.

In the above-mentioned preferable embodiment, especially in case thatthe solid particle contains surface adhesive water, the reaction is asfollows. That is to say, the reaction is between CO₂ in the exhaust gasand the solid particle. In other words, the reaction is between a Cacomponent (Ca ion) dissolving (diffusion) into the surface adhesivewater from the solid particle and carbon dioxide component dissolvedinto the water content adhered on the surface out of the exhaust gas. Itwas found that the reaction with CO₂ in the surface adhesive water ofthe solid particle was especially effective for absorbing and fixingCO₂.

At first, the inventors considered that in a method of reacting CO₂ inan exhaust gas with Ca in solid particles for fixing CO₂ as CaCO₃ in thesolid particles, CaCO₃ would be precipitated on the whole surface of thesolid particles as the reaction progressed, and as a result ofpreventing the diffusion of Ca ions from the solid particles, a CO₂absorbing efficiency of a high level to be practiced on an industrialscale could not be expected. However, absolutely contrary to theirexpectations, it was found that if the reaction with CO₂ was carried outunder the condition where the water content existed in the solidparticles, in particular under the condition where the water was adheredto the surface of the solid particles, CO₂ could be absorbed at anextremely high efficiency. The reasons therefore are not clear, however,the following reasons may apply.

FIG. 1 is a schematic view, which assumes a mechanism of absorbing andfixing CO₂ in the exhaust gas in the surface of the solid particles. Asseen in FIG. 1, under the condition where adhesive water exists on thesurface of the solid particles containing CaO, Ca ions are dissolvedfrom the solid particles into the surface adhesive water, while CO₂(carbon ions) is dissolved from the exhaust gas into the surfaceadhesive water, respectively. Both of Ca ions and carbon ions react inthe surface adhesive water. Furthermore, CaCO₃ is precipitated mainly inthe surface of the solid particles. When precipitating, theprecipitating nucleus of CaCO₃ is not uniformly generated in water,nucleus of CaCO₃ is not uniformly generated in water, however, it isgenerated as a non-uniform nucleus which is easily generated in thesurface of the solid particles. Therefore, the precipitation of CaCO₃and growth thereafter occurs merely in the specific area on the surfaceof the solid particles. Consequently, it is considered that there canexist, at a considerable proportion, a surface area of the solidparticles where neither precipitation nor growth of CaCO₃ takes place.Since it is possible to maintain the supply (dissolution) of Ca ions inthe surface adhesive water of the solid particles, CO₂ can beeffectively absorbed and fixed in a short period.

Further reference will be made to the preferable embodiment of theinvention.

The present embodiment uses, as the CO₂ absorbing material, anagglomerate of solid particles containing CaO and/or Ca(OH)₂ as thecomposition. Ca(OH)₂ contained in the solid particles also reacts withCO₂ similarly to CaO. Since it can be fixed as CaCO₃, the solidparticles may contain Ca(OH)₂. As mentioned above, CaO and Ca(OH)₂contained in the solid particles are sufficient with such substancescontained as a part of the composition of at least the solid particle,and therefore, substances other than CaO and Ca(OH)₂ as minerals areincluded which exist in the solid particles as parts of the compositionsuch as 2CaO.SiO₂, 3CaO.SiO₂ or glass.

As such solid particles, in particular concrete containing much CaO(and/or Ca(OH)₂) or slag generated in the iron-steel making process aredesirable. Reference will be made in detail later therefore.

Grain sizes of the solid particles are not especially limited, howeverthe grain sizes which are as small as possible are preferable forsecuring to contact areas with the exhaust gas and increasingreactivity, specifically substantially 5 mm or lower (excepting solidparticles of a large size inevitably included), in particular preferably1 mm or less. Actually, it is preferable that grains of 5 mm or lessoccupy 90% or more.

As mentioned above, for securing the reactivity between the solidparticles and CO₂ in the exhaust gas in the exemplified method, it ispreferable that the main solid particles contacting the exhaust gascontain the appropriate amount of water. It is more desirable that themain solid particles contacting the exhaust gas have the surfaceadhesive water thereof. Surface adhesive water means the water contentexisting together with the solid particles and the water existing in theouter surface of the solid particles, except the water content containedwithin the grains. Preferably, the percentage of water content in theagglomerate of the solid particles is 3 to 20% from a similar viewpoint.Thus, for maintaining the water content of the solid particles and theagglomerate thereof, the water content is, as needed, previously addedto the agglomerate of the solid particles.

The CO₂ containing exhaust gas to be contacted with the agglomerate ofsolid particles heightens reactivity with the solid particles byincreasing the temperature thereof, to some extent. However, if thetemperature of the exhaust gas to be introduced into the space (calledas “reaction space” hereinafter) for contacting with the agglomerate ofsolid particles exceeds the boiling point of water supported in thereaction space, it evaporates the surface adhesive water of the solidparticles, and hinders the reactivity. Therefore, it is preferable thatthe temperature of the exhaust gas is set to be at the boiling point ofwater or lower in the reaction space. Also for the same reason,preferably the temperature within the reaction space is kept at theboiling point of water or lower and, in addition, the temperature of theagglomerate of solid particles is also kept at the boiling point ofwater or lower within the reaction space.

From a similar viewpoint, it is preferable to have a higherconcentration of steam in the exhaust gas, and so, it is desirable thatH₂O is saturated by an instrument by previously passing the exhaust gasin water, and subsequently the exhaust gas is contacted with theagglomerate of solid particles.

As the agglomerate of solid particles to be the CO₂ absorbing material,as far as being the agglomerate of solid particles containing CaO and/orCa(OH)₂, no limit is provided, however in particular, in points that thecontaining rate of CaO (and/or Ca(OH)₂) is high and a recycle ofmaterials is available, slag generated in the iron-steel making process,and concrete (for example, waste concrete) are desirable. Accordingly,preferably, at least one part of the solid particle comprising theagglomerate of solid particles is slag and/or concrete and, as isespecially desirable, the main solid particles are slag and/or concrete.

As the agglomerate of solid particles to be the CO₂ absorbing material,other than slag and concrete, there may be listed mortar, glass, aluminacement, CaO containing refractory, or MgO containing with refractory,and one kind or more of the agglomerate of solid particles may be singlymixed, otherwise mixed with slag and/or concrete.

The agglomerate of solid particles has a better reactivity with CO₂ ifthe weight ratio (basicity) of CaO to SiO₂ is high, and from thisviewpoint, it is preferable that CaO/SiO₂ is 1.2 or higher and,desirably, 1.5 or higher.

In general, the composition of CaO in the slag generated in theiron-steel making process is about 13 to 55 wt. %, and the compositionof CaO in the concrete (e.g. waste concrete) is about 5 to 15 wt. % (theCaO composition in the cement: 50 to 60 wt. %), and being easilyavailable, they are well-suited materials as the solid particles to bethe CO₂ absorbing material.

As slag generated in the iron-steel making process, there may beenumerated slags from blast furnaces such as a slow cooling slag or awater granulated slag therefrom, which means slags from the iron-steelmaking process such as dephosphorized slag, desulfurized slag,desiliconized slag, decarburized slag or casting slag generated inpre-treatments, converter or casting slags from iron ore reduction; orslags from electric furnaces. However, there is no limit to the types ofslags. Slag mixtures of two kinds or more may be used.

Slag generated in the iron-steel making process contains a considerableamount of iron (grain iron). If the agglomerate of solid particles ofsuch slag is used as it is, since the CaO composition in the agglomerateof solid particles is lowered by the amount of the iron content, it ispreferable to use slag having passed through a metal (iron) recoverytreatment. The metal (iron) recovery treatment is generally carried outfor recycling the iron content in slag to the iron-steel making process,and ordinarily slag is crushed for recovering the metal therein, and aconsiderable amount of the iron content is recovered and removed fromslag by means such as a magnetic separation.

As a concrete, for example, waste concrete may be used which are made bydestroying buildings or from civil engineering projects.

These materials are crushed into grain like or grain as needed and usedas the agglomerate of solid particles.

As mentioned above, in the agglomerate of solid particles to be the CO₂absorbing material, it is preferable that the basicity be high, forexample, ane agglomerate of solid particles where the basicity is lessthan 1.5 as the water granulated slag, has a poor solubility of Ca ion,and is low in the reactivity with CO₂, and therefore it may not be saidthat the function as the CO₂ absorbing material is fully exhibited. Thisis why solid particles having a low basicity have a small amount ofcalcium silicate to be carbonized (e.g., 2CaO.SiO₂ or 3CaO.SiO₂), orhave much glass as the water granulated slag.

Therefore, when utilizing, as the CO₂ absorbing material, an agglomerateof solid particles having a low basicity (ordinarily the basicity isless than 1.5), it is preferable to mix them with solid particles havinga high basicity to be an alkaline stimulating agent for heightening thesolubility of Ca ions from the solid particles having a low basicity,preferably an agglomerate of solid particles having a basicity being 1.8or higher, adding water thereto (preferably after an air wetting cure(hydration cure)), and employing the thus obtained mixture as the CO₂absorbing material. The solid particles having a high basicity of 1.8 orhigher, act as an alkaline stimulating agent to the solid particles ofhaving a low basicity under the existence of the water content, andaccelerate the hydration of solid particles having a low basicity.

For example, in the case of a solid particle having lower contents ofcalcium silicate and CaO, the hydration of calcium silicate and CaOwithin the solid particle is accelerated by the alkaline stimulatingagent, and as a result, Ca ions are ready to be dissolved from the solidparticle and, even if a solid particle is per se less in calciumsilicate and CaO, the dissolution of Ca ions is heightened as a whole.In addition, in the case of a solid particle having much glass, asilicate network forming the glass by ane alkaline stimulating agent isbroken, and simultaneously the hydration thereof is accelerated,resulting in increasing the CaO content enabling carbonation.

Further, it is useful for heightening the CO₂ absorbing efficiency toprepare a condition of easily carbonating CaO by advancing the hydrationeffected by an air wetting cure (hydration cure) after the wateraddition. Namely, since a certain period of time is needed for thedissolution of alkali, by only mixing only solid particles of a lowbasicity and solid particles of a high basicity and by simply addingwater, it is insufficient to effectively heighten the solubility of Caions of the solid particles having a low basicity. Therefore, desirably,after mixing the agglomerates of both solid particles, an air wettingcure is performed for a requisite period of time.

Such an air wetting cure brings about, as mentioned later, introductionof cracks into the solid particles or a refining effect of the solidparticles, and also as a result, the CO₂ absorbing ability of the solidparticles is increased.

The air wetting cure may be carried out by a simple method of, forexample, mixing an agglomerate of solid particles having a high basicityand an agglomerate of solid particles having a low basicity, kneadingthe mixture under the existence of an appropriate amount of watercontent, and covering the mixture with a vinyl sheet. However, forpreventing carbonation of the solid particles during curing, it ispreferably carried out under an atmosphere substantially not containingCO₂, otherwise under an atmosphere substantially not supplied with CO₂during at least curing, and accordingly, for example, in a space(atmosphere) cutting off the atmosphere. CO₂ contained in theatmospheric air exists at first in such a space, however more CO₂ is notsupplied.

The time period for the air wetting cure is not especially limited,however, for obtaining desirable effects by the air wetting cure,practicing an air wetting cure for more than 12 hours, desirably 24hours is preferable.

After practicing the air wetting cure, the mixture may be pulverized foruse as the CO₂ absorbing material. By the pulverizing treatment, thecontacting area with the exhaust gas containing CO₂ is increased, andthe reactivity with CO₂ is heightened.

Further reference will be made to an effective method for heighteningthe CO₂ absorbing ability of the solid particles.

The solid particles (for example, waste concrete or slag generated inthe iron-steel making process) to be used as the CO₂ absorbing materialis generally massive or grain, and since it takes a long time forreacting with CO₂ until an interior of the solid particles, a CaO sourceat the interior of the solid particle trends to be less usefully usedfor absorption of CO₂. For solving this problem, it is useful to subjectthe massive or grain solid particles to the air wetting cure (hydrationcure) so as to effect hydration expansion and, by this hydrationexpansion, cracks are introduced into the solid particle. Otherwise,breakage occurs from this crack into fine grains and, as the surfacearea of the solid particle to be contacted with CO₂ is increased, theabsorbing effect of CO₂ by the CaO source is effectively improved.Further, it is possible to change a CaO containing substance in thesolid particles to be a hydrated substance being ready for a carbonatingreaction by the air wetting cure and also, as a result, the absorbingeffect of CO₂ by the CaO source is increased.

When the agglomerate of solid particles is hydration-expanded by the airwetting cure, preferably the agglomerate of solid particles is laid inan atmosphere substantially not containing CO₂, otherwise in anatmosphere substantially not supplied with CO₂ during at least curing,and the air wetting cure is performed under the existence of the water.For supplying a water content to the agglomerate of solid particles,there is a method of adding water or warm water to the agglomerate ofsolid particles before and/or after laying the agglomerate of solidparticles in the space for the air wetting cure, or a method of blowingsteam to the agglomerate of solid particles laid in the space for theair wetting cure.

The reason why the air wetting cure is carried out in an atmospheresubstantially not containing CO₂, otherwise in an atmospheresubstantially not supplied with CO₂ during at least curing, is becausethe solid particles do not cause the carbonating reaction, preferably,for example, in a space (atmosphere) cutting off the atmosphere. CO₂contained in the atmospheric air exists at first in such a space,however more CO₂ is not supplied.

When adding warm water to the agglomerate of solid particles, 60° C. orhigher is desirable from the viewpoint of effective curing.

The agglomerate of solid particles having passed the air wetting curemay serve as the CO₂ absorbing material.

There is no special restriction in the actual means for contacting theexhaust gas with the agglomerate of solid particles, however thefollowing may be exemplified as suitable treating systems in aspects oftreating efficiency or ease of handling the agglomerate of solidparticles.

(1) A system of contacting the exhaust gas with an agglomerate of solidparticles in a fluidized bed using the exhaust gas as a fluidizing gas.

(2) Another system of contacting the exhaust gas with an agglomerate ofsolid particles in a rotary kiln.

(3) A further system of forming a layer filled up with an agglomerate ofsolid particles, supplying the exhaust gas in the packed bed, thereby tocontact the exhaust gas and the agglomerate of solid particles.

FIG. 2 shows one practiced embodiment of the above (1) system, whereinreference numeral 1 designates a processing container furnished with agas dispersing plate 100 at a lower part and structured thereon with aspace A for forming the fluidized bed, 2 is a device for supplying anagglomerate of solid particles in the processing container 1, 3 is aconduit for supplying the exhaust gas containing the CO₂ into theprocessing container 1 (a wind box 110 below the dispersing plate 100),4 is a conduit for issuing the exhaust gas from the processing container1, and 5 is a solid particle exhausting pipe for taking out anagglomerate of solid particles in the processing container 1 from timeto time.

According to this treating system, the agglomerate of solid particlessuch as slag or concrete is supplied from the supply device 2 into thespace A of the processing container 1, while the exhaust gas suppliedfrom the gas supply conduit 3 into the wind box 110 is blown out intothe space A from the gas dispersion plate 100, and the fluidized bed ofthe agglomerate of solid particle is formed. In the fluidized bed, thesolid particles and CO₂ in the exhaust gas are reacted, and CO₂ is fixedas CaCO₃ to the solid particles. The exhaust gas having finished thisreaction is discharged from the processing container 1 through the gasdischarging conduit 4, and the solid particles within the processingcontainer 1 is also discharged from the solid particle discharging pipe5 in response to the degree (CO₂ absorbing ability) of absorbing CO₂.

A plurality of processing containers are installed as shown withtwo-doted lines in FIG. 2 and, if the exhaust gas issuing conduits areconnected in series to said plurality of chambers 1, 1 a, 1 b . . . , inother words, if the exhaust gas is successively treated through theplurality of processing containers installed in series in such a mannerthat the exhaust gas from the processing container 1 is supplied to thechamber 1 a, and the exhaust gas from the chamber 1 a is sent to thechamber 1 b, it is possible to effectively curtail CO₂ in the exhaustgas.

The form of the fluidized bed for the treating system (1) is arbitraryand is not limited to that of FIG. 2.

FIG. 3 shows one practiced embodiment of the above (2) system, whereinreference numeral 6 designates a rotary kiln, 7 is a device forsupplying the agglomerate of solid particles into the rotary kiln 6, 8is a gas supply conduit for supplying the exhaust gas containing CO₂into the rotary kiln, 9 is a gas discharging conduit for issuing theexhaust gas from the rotary kiln 6, and 10 is a solid particleexhausting pipe for taking out the agglomerate of solid particles withinthe rotary kiln.

According to this treating system, the agglomerate of solid particlessuch as slag or concrete is supplied from the supply device 7 into atreating space of the rotary kiln 6, while the exhaust gas is suppliedfrom the gas supply conduit 8, and the agglomerate of solid particlesreacts with CO₂ in the exhaust gas as being mixed in the rotary kiln 6,and CO₂ is fixed as CaCO₃ to the solid particles. The exhaust gas havingfinished this reaction is discharged from the rotary kiln 6 through thegas discharging conduit 9, and the solid particles having reached anexit of the rotary kiln 6 are also discharged from the solid particledischarging pipe 10.

Also in this system, a plurality of rotary kilns are installed as shownwith two-doted lines in FIG. 3, and if the exhaust gas issuing conduitsare connected in series to said plurality of rotary kilns 6, 6 a, 6 b,in other words, if the exhaust gas is successively treated through theplurality of rotary kilns installed in series in such a manner that theexhaust gas from the rotary kiln 6 is supplied to the rotary kiln 6 a,and the exhaust gas from the rotary kiln 6 a is sent to the rotary kiln6 b, it is possible to effectively curtail CO₂ in the exhaust gas.

The form of the rotary kiln for the treating system (2) is arbitrary,and is not limited to that of FIG. 3.

FIG. 4 shows one practiced embodiment of the above (3) system, whereinreference numeral 11 designates a closed or a half closed type containerfor forming a layer filled up by the agglomerate of solid particles, 12is a gas supply conduit for blowing the exhaust gas containing CO₂ intothe container 11, and 13 is a gas discharging conduit for issuing theexhaust gas from the container 11.

According to this treating system, the agglomerate of solid particles ischarged into the container 11 to form a layer filled up thereby, towhich the exhaust gas is supplied from the gas supply conduit 12, andwhile the exhaust gas flows through the packed bed, CO₂ in the exhaustgas reacts with the solid particles, and CO₂ is fixed as CaCO₃ to thesolid particles. The exhaust gas having finished this reaction isdischarged from the container 11 through the gas discharging conduit 13.In this system, since the agglomerate of solid particles in thecontainer 11 is not fluidized as the fluidized bed, ordinarily solidparticles are massively combined with one another by carbonatingreaction. Therefore, after having processed for a certain period oftime, the agglomerate of combined solid particles is taken out from thecontainer 11, and subsequently the agglomerate of new solid particles ischarged into the container 11.

Also in this system, a plurality of containers are installed as shownwith two-doted lines in FIG. 4, and if the exhaust gas issuing conduitsare connected in series to said plurality of containers 11, 11 a, 11 b .. . , in other words, if the exhaust gas is successively treated throughthe plurality of containers installed in series in such a manner thatthe exhaust gas from the container 11 is supplied to the container 11 a,and the exhaust gas from the container 11 a is sent to the container 11b, it is possible to effectively curtail CO₂ in the exhaust gas.

The form of the container for the treating system (3) is arbitrary, andis not limited to that of FIG. 4.

In this treating system (3), if the filling rate of the agglomerate ofsolid particles in the packed bed is small, the exhaust gas becomes lessto contact with the solid particles to affect influences with respect tothe treating efficiency, and it is preferable that the filling rate ofthe agglomerate of solid particles is 40 to 90 vol. %, desirably 50 to75 vol. %.

The CO₂ composition in the exhaust gas contacting with the agglomerateof solid particles also governs the treating efficiency, and if it istoo low, the treating efficiency is decreased. For efficiently removingCO₂ in the exhaust gas, the CO₂ concentration should be more than 5%(preferably 10% or higher). As the exhaust gases, there are listedexhaust gases from CaCO₃, a calcination furnace, a hot blast furnace, aboiler, a coke oven, a sintering furnace, a slab heating furnace or anannealing furnace.

In the characteristics of the method of this embodiment, there is noproblem that the exhaust gas of relatively low CO₂ concentration is tobe treated by the method of this embodiment.

For heightening the treating efficiency, it is preferable that theexhaust gas to be supplied into the treating space is pressurized. Thegas pressure is not especially limited, however since the higher thepartial pressure of CO₂, the higher the dissolving speed of CO₂ into thesurface adhesive water of solid particles, if CO₂ is contacted with theagglomerate of solid particles under the condition that CO₂ ispressurized, the treating efficiency can be heightened in comparisonwith contacting at atmospheric pressure.

The exhaust gas containing CO₂ to be treated by the present embodimentincludes gases containing CO₂ issued from various kinds of facilities orequipment, and these exhaust gases (exhaust gases containing CO₂) are ofcourse not limited. The exhaust gas containing CO₂ to be treated by thepresent embodiment includes, for example, gas generated in theiron-steel making process and utilized as fuel gas, so-called secondarygas (for example, gases from a blast furnace, converter or coke oven),irrespective of which is a combustion exhaust gas or a gas usable asfuel. Various kinds of exhaust gases generated from an iron making firmgenerally include CO₂ of high concentration, and as mentioned above,since the amount of the final energy consumption by all the iron andsteel firms accounts for about 11% of the whole of Japan, the method ofthis embodiment may be said to be very useful for the treatment of manykinds of exhaust gases particularly generated from the iron making firms(the iron-steel making process).

As the secondary gas caused in the iron-steel making process such as ablast furnace, converter or coke oven has a high caloric value, it isused as a fuel gas. On the other hand, CO₂ is relatively substantiallyincluded in these exhaust gases (secondary gases), and is exhausted intothe atmospheric air by and by (after having been used as fuel), acaloric value as the fuel gas is lowered by an amount containing CO₂,the amount of using the fuel gas is correspondingly increased by theamount of lowering the caloric value, and as a result the amount ofgenerating CO₂ is increased.

Accordingly, in the method of this embodiment, it is possible to makethe fuel gas high in calories and cut the amount of generating CO₂ intotal together while decreasing the amount of the fuel gas used.

Further reference will be made to the preferable embodiment of theinvention.

[a1] The method of reducing exhaust carbon dioxide, wherein at least onepart of said agglomerates of solid particles is a slag generated in aniron-steel making process, and/or concrete.

[a2] The method of reducing exhaust carbon dioxide, wherein the solidgrain comprising the agglomerates of solid particles is a slag generatedin iron-steel making processes, and/or concrete.

[b] The method of reducing exhaust carbon dioxide, wherein theagglomerates of solid particles comprise at least one selected from thegroup consisting of concrete, mortar, glass, alumina cement, CaOcontaining refractories, and a slag generated in the iron-steel makingprocess.

Other embodiments may be enumerated as follows.

[c] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] (the method of [1] to [14] described in the“Summary of the Invention”), characterized in that the slag is a slagwhich has passed a metal recovering treatment.

[d] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [c], characterized in that weightratio of CaO/SiO₂ of the agglomerates of solid particles to be contactedwith the exhaust gas containing CO₂ is 1.2 or higher.

[e] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [d], characterized in that the exhaustgas containing CO₂ and the agglomerates of solid particles are contactedwithin a fluidized bed, wherein the exhaust gas serves as a gas forfluidizing.

[f] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [d], characterized in that the exhaustgas and the agglomerates of solid particles are contacted within arotary kiln.

[g] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [d], characterized by forming a packedbed which is filled with the agglomerates of solid particles, andsupplying the exhaust gas into said packed bed, thereby to contact theexhaust gas with the agglomerates of solid particles.

[h] The method of reducing exhaust carbon dioxide as set forth in theabove [g], characterized by blowing the exhaust gas into said packedbed, thereby to contact the exhaust gas with the agglomerates of solidparticles.

[i] The method of reducing exhaust carbon dioxide as set forth in theabove [h], characterized by blowing said exhaust gas into theagglomerates of solid particles from one direction, thereby to contactthe exhaust gas with the agglomerates of solid particles.

[j] The method of reducing exhaust carbon dioxide as set forth in theabove [g], characterized in that the packing ratio of the agglomeratesof solid particles in the packed layer is 40 to 90 vol. %.

[k] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [j], characterized in that theconcentration of CO₂ in the exhaust gas to be contacted with theagglomerates of solid particles is 5% or more.

[l] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [k], characterized in that theagglomerates of solid particles where the weight ratio of CaO to SiO₂ isless than 1.5 and the agglomerates of solid particles where the weightratio of CaO to SiO₂ is 1.8 or more, are mixed, and contacted with theexhaust gas containing CO₂ under a condition where the mixture is addedwith the water content.

[m] The method of reducing exhaust carbon dioxide as set forth in theabove [l], characterized in that the agglomerates of solid grain of theweight ratio of CaO to SiO₂ being less than 1.5 are a water granulatedslag from a blast furnace.

[n] The method of reducing exhaust carbon dioxide as set forth in theabove [l] or [m], characterized in that the agglomerates of solidparticles where the weight ratio of CaO to SiO₂ is less than 1.5 and theagglomerates of solid particles where the weight ratio of CaO to SiO₂ is1.8 or more, are mixed, and performed with an air wetting curing.

[o] The method of reducing exhaust carbon dioxide as set forth in theabove [n], characterized by operating a hydration curing for 12 hours ormore.

[p] The method of reducing exhaust carbon dioxide as set forth in theabove [n] or [o], characterized in that the agglomerates of solidparticles are performed with the air wetting curing, and then crushed.

[q] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [q], characterized in that theagglomerates of solid particles are performed with the air wettingcuring so that the solid particles are hydration-expanded, thereby to befinely crushed by cracking and/or breaking, and the agglomerates ofsolid particles after the air wetting curing is contacted with theexhaust gas containing CO₂.

[r] The method of reducing exhaust carbon dioxide as set forth in theabove [q], characterized by performing the air wetting curing in anatmosphere substantially not containing CO₂ or an atmosphere beingsubstantially not supplied with CO₂ during at least curing.

[s] The method of reducing exhaust as set forth in the above [q] or [r],characterized by adding water or warm water to the agglomerates of solidparticles to be performed with the air wetting curing.

[t] The method of reducing exhaust carbon dioxide as set forth in theabove [s], characterized in that the temperature of the warm water to beadded to the agglomerates of solid particles is 60° C. or higher.

[u] The method of reducing exhaust carbon dioxide as set forth in theabove [q] or [s], characterized by blowing steam into the agglomeratesof solid particles to be performed with air wetting curing.

[v] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [u], characterized in that the exhaustgas containing CO₂ is an exhaust gas generated in the iron-steel makingprocess.

[w] The method of reducing exhaust carbon dioxide as set forth in any ofthe above [1] to [14] and [a1] to [u], characterized in that the exhaustgas containing CO₂ is an exhaust gas to be used as fuel gas.

[x] The method of reducing exhaust carbon dioxide as set forth in theabove [w], characterized in that the exhaust gas to be used as the fuelgas is a secondary gas (for example, one or two kinds of gases from theblast furnace, converter and coke oven) generated in the iron-steelprocess.

Further reference will be made to Examples relating to theabove-mentioned embodiments.

EXAMPLE 1

A pipe shaped reactor of 2 m length having an inlet and an outlet forthe exhaust gas at both ends was filled with the slag (grain size: 10 mmor lower, CaO: 35 wt. %, water content: 6%, packing ratio: 50 vol. %) .The packed bed was supplied with the exhaust gas (CO₂ concentration:20%, temperature: 40° C.) at the gas pressure: 0.3 kgf/cm²-G for 24hours, and as a result of measuring the CO₂ absorbing amount by theslag, the absorbed CO₂ was about 0.2 at value of CO₂/slag.

Being based on this CO₂ absorbing amount, when the CO₂ absorbing amountin a real machine was calculated by trial, the calculation meant that itwas possible to absorb CO₂ of 15,000 t/year (in terms of C), using200,000 t/year of slag.

EXAMPLE 2

Prepared were the as-slowly cooled dephosphorized slag of 48 wt. % CaO,and the slag where said dephosphorized slag was charged in a steel-madecontainer, blown with steam under the condition of cutting off the air,and performed with an air wetting cure (hydration cure).

The cured slag and the non-cured slag were passed through a 20 mm screento produce grain like slags of −20 mm size. These slags wereinvestigated with respect to the ratio of grain like slags of −5 mm,using a 5 mm screen.

The above cured slag and the non-cured slag of −20 mm grain size wererespectively adjusted to be the 6% water content, and charged 2 kg intothe molds (100 mm×200 mm), and blown with carbon dioxide (CO₂concentration: 20%, temperature: 25° C.) 2 liter/min for 24 hours fromthe mold bottoms, and the slags were recovered to measure the CO₂absorbing (fixing) amount.

The results are shown in Table 1. According to the results, in Examples2-1, cracks were introduced in the slag grain by the hydration expansionowing to the air wetting cure, and in comparison with the non-curedslag, the ratio of fine slag of −5 mm or smaller increased by 10 wt. %,and as seen from this, cracks occurred in the slag grains by hydrationexpansion, so that, when using the cured slag, the CO₂ absorbingefficiency was more heightened than Example 2-2, and more CO₂ could beabsorbed. TABLE 1 Examples Treating conditions 2-1 Examples Hydrationcuring time (hr) 24 0 Carbon dioxide passing time 24 24 Slag amount (wt.%) of −5 mm before 50 40 supplying carbon dioxide CO₂ absorbing (fixing)amount (wt. %) 14 6

In relation with the above mentioned first embodiment, a secondembodiment is concerned with a sea-water immersion block, a method ofmaking the same, a river water immersion block, a method of making thesame, and a method for providing algae planting places. Reference willbe made thereto.

Immersion Block in Sea-water

The inventors made experiments and investigations, and as a result, theyfound the following facts.

(1) Grain like slags, rough grain like slags or small massive slags, inparticular such slags moderately containing an iron content areconsolidated with a binder of CaCO₃ or CaCO₃ and MgCO₃ produced by acarbonating reaction, and the thus consolidated massive slag is used assea water-immersion blocks, thereby displaying excellent effects in therearing of marine algae without increasing the pH of the sea water.

(2) On the other hand, for a sea area which necessitates to control fora shortage of oxygen in the sea water owing to the oxidation of ironcontent or an excessive supply of iron content into the sea water, thegrain-like or the rough grain like slags having passed the metalremoving treatment are consolidated with a binder of CaCO₃ or CaCO₃ andMgCO₃ produced by a carbonating reaction. The thus consolidated massiveslag is used as sea water-immersion blocks, thereby displaying excellenteffects in the rearing of marine algae without causing a shortage ofoxygen in the sea water owing to oxidation of iron content or anexcessive supply of iron content into the sea water or increasing the pHof the sea water.

(3) For obtaining the massive immersion block in the sea water asmentioned above, such a production method is useful which consolidatesthe above mentioned slags by piling or packing at a desired compositionof at least one slag selected from the group of the grain like slag, therough grain like slag and the small massive slag, otherwise the grainlike or rough grain like slag having passed the metal removingtreatment, and by causing a carbonating reaction in the piled or packedbed under the existence of carbon dioxide. According to this productionmethod, it is possible to produce blocks of arbitrary density and sizein response to conditions of sea bottoms or ocean currents to be appliedwith blocks.

The present embodiment has been practiced based on the above mentionedfindings, and is characterized as follows.

(1) The embodiment is concerned with immersion blocks in the sea of amain raw material being a slag generated in the iron-steel makingprocess, consolidating the slag with a binder of CaCO₃ produced bycarbonating reaction, and making the slag massive. This slag is at leastone selected from the group of the grain like slag, the rough grain likeslag and the small massive slag. The present slag is sufficient withgrain like or rough grain like slag having passed a metal removingtreatment.

(2) The embodiment is concerned with immersion blocks in the sea of amain raw material being a slag generated in the iron-steel makingprocess, consolidating the slag with a binder of CaCO₃ and MgCO₃produced by a carbonating reaction, and making the slag massive. Theembodiment includes a case where MgCO₃ exists as a hydrate, hydroxidesalt or double salt. This slag is at least one selected from the groupof the grain like slag, the rough grain like slag and the small massiveslag. The present slag is sufficient with grain like or rough grain likeslag having passed a metal removing treatment.

(3) The embodiment is concerned with immersion blocks in the sea of mainraw materials being a slag generated in the iron-steel making process,grain like additives and/or rough grain like additives, consolidating amixture of the slag and the additives with a binder of CaCO₃ produced bya carbonating reaction, and making the slag massive. This slag is atleast one selected from the group of the grain like slag, the roughgrain like slag and the small massive slag. The present slag issufficient with grain like or rough grain like slag having passed ametal removing treatment.

(4) The embodiment is concerned with immersion blocks in the sea of mainraw materials being a slag generated in the iron-steel making process,grain like additives and/or rough grain like additives, consolidating amixture of the slag and the additives with a binder of CaCO₃ and MgCO₃produced by a carbonating reaction, and making the slag massive. Theembodiment includes a case where MgCO₃ exists as a hydrate, hydroxidesalt or double salt. This slag is at least one selected from the groupof the grain like slag, the rough grain like slag and the small massiveslag. The present slag is sufficient with grain like or rough grain likeslag having passed the metal removing treatment.

(5) A method of making immersion blocks in the sea water ischaracterized in that the slag generated in the iron-steel makingprocess is, as needed, mixed with one kind or more selected from CaO,Ca(OH)₂, MgO and Mg(OH)₂, and the slag is piled, or the packed bed isformed in an arbitrary space, and is subjected to a carbonating reactionunder the existence of carbon dioxide so as to consolidate the slag forproviding blocks of the massive slag. This slag is at least one selectedfrom the group of the grain like slag, the rough grain like slag and thesmall massive slag. The present slag is sufficient with grain like orrough grain like slag having passed a metal removing treatment.

(6) A method of making immersion blocks in the sea water ischaracterized in that the slag generated in the iron-steel makingprocess is mixed with grain like additives and/or rough grain additivesand is, as needed, mixed with one kind or more selected from CaO,Ca(OH)₂, MgO and Mg(OH)₂, and the slag is piled or the packed bed isformed in an arbitrary space, and is subjected to a carbonating reactionunder the existence of carbon dioxide so as to consolidate the slag forproviding blocks of the massive slag. This slag is at least one selectedfrom the group of the grain like slag, the rough grain like slag and thesmall massive slag. The present slag is sufficient with grain like orrough grain like slag having passed the metal removing treatment.

(7) In the embodiments (1) to (6), one part or all of the slag generatedin the iron-steel making process may be replaced with a CaO containingmaterial (for example, waste concrete).

The present embodiment is concerned with the immersion blocks in theseawater of a main raw material being a slag generated in the iron-steelmaking process. As the slag generated in the iron-steel making process,there may be enumerated slags from blast furnaces such as a slowlycooled slag or a water granulated slag therefrom. That is to say, slagsfrom the iron-steel making process such as dephosphorized slag,desulfurized slag, desiliconized slag, decarburized slag or casting slaggenerated in pre-treatments, converter or casting; slags from iron orereduction; or slags from electric furnaces. However, no limit isprovided to them. Slag mixtures containing two kinds or more of slag maybe used.

Of these slags, the compositions of representative ones will beexemplified as follows.

(1) Decarburized slag . . . T.Fe: 17.5%, CaO: 46.2%, SiO₂: 11.7%, Al₂O₃:1.4%, MgO: 8.3%, MnO: 6.2%, P: 0.76%, S: 0.04%

(2) Dephosphorized slag . . . T.Fe: 5.8%, CaO: 54.9%, SiO₂: 18.4%,Al₂O₃: 2.8%, MgO: 2.3%, MnO: 1.9%, P: 2.8%, S: 0.03%

(3) Desulfurized slag . . . T.Fe: 10.5%, CaO: 50.3%, SiO₂:10.0%, Al₂O₃:5.4%, MgO: 1.1%, MnO: 0.4%, P: 0.13%, S: 1.8%

(4) Desiliconized slag . . . T.Fe: 10.5%, CaO: 13.6%, SiO₂: 43.7%,Al₂O₃: 3.8%, MgO: 0.4%, MnO: 15.8%, P: 0.10%, S: 0.19%

(5) Water granulated slag: T.Fe: 0.3%, CaO: 42.0%, SiO₂: 33.8%, MnO:0.3%, MgO: 6.7%, Al₂O₃: 14.4%

Incidentally, among the slags generated in the iron-steel makingprocess, the dephosphorized slag is high in P content and thedesiliconized slag is high in MnO. Therefore, those are difficult to beused as raw materials for cement. However, the invention can make use ofthem as main raw materials of the sea water-immersion blocks with noaccompanying problem involved therewith.

The slags generated in the iron-steel making process as mentioned abovecontain relatively much metal (iron content as grain iron) though moreor less (ordinarily, around several wt % to 30 wt %), and metals inslags are pulverized to recover for recycling the iron content to theiron-steel making process. Accordingly, including the grain like, roughgrain like or small massive slags, the slags having passed the metalrecovering process are necessarily the grain like, rough grain like orsmall massive slags. Ordinarily, grain sizes of the slag having passedthe metal recovering process are at cm-order or smaller (for example, 5cm or smaller).

The present embodiment employs at least one of these grain like, roughgrain like or massive slags for sea water-immersion blocks.

The slag to be employed in the embodiment is sufficient with at leastone of the grain like, rough grain like or massive slags, and it is nota necessary condition to pass the metal recovery treatment.

Herein, by the metal recovery treatment is meant a treatment foryielding metals from slags aiming at recycling metals contained inslags, and this is different from a treatment for substantially removingmetals in slags as the metal removing treatment. Therefore, the slag inthe metal recovery treatment is not pulverized finely as in the metalremoving treatment, and so the treated slag still contains much metal.On the other hand, by the metal removing treatment is meant a treatmentwhich finely pulverizes the slag in grain like or rough grain like andremoves all metals except inevitably remaining ones.

When these slags are rendered to be raw materials of sea water-immersionblocks, the iron containing amount is not required to be low as in thecase where the slag having passed the later mentioned metal removingtreatment is rendered to be a raw material of block. Rather, it isbetter that the iron content of a proper amount (particularly, metalliciron or alloyed iron material such as grain iron) is contained in slag.This is why the iron content contained in the slag in a proper amount isdissolved in the sea water, so that the iron content is supplied as anutrient salt in the sea water, and this usefully works for rearingmarine algae. Thus, the iron content in slag is appropriately 3-wt % ormore.

The iron content in slag is adjusted by the following two methods.

(a) The metal (such as grain iron) contained per se in slag is utilizedas it is, not recovering parts or all but leaving it to remain.

(b) All of the substantial parts of the metal in slag (excepting themetal, which cannot inevitably be removed) are removed through the metalremoving treatment and are added with metallic iron or metal containingiron materials as additives.

Depending on the method (b), the following merits are brought about.

(1) In the method (a) which leaves the metal (such as grain iron)contained per se in slag is utilized as it is, not recovering one part,it is difficult to correctly adjust the amount of the metal remaining inslag. Namely, the metal recovery from slag is carried out by a magneticseparation, and owing to the nature of the magnetic separation, it isvery difficult to recover the metal, leaving the metal of a certainamount in slag. If possible, a troublesome control or operation isrequired for carrying out the magnetic separation. On the other hand, inthe method (b), since all of the substantial parts of the metal per secontained in slag are removed and anew added with the metallic iron orthe metal containing iron materials as additives, the iron content inslag can be arbitrarily controlled.

(2) For the same reason as above, the method (a) which leaves the metal(such as grain iron) contained per se in slag, not recovering parts,cannot select shapes or sizes of the metal in slag. As later mentioned,what is preferable in general is so-called grain iron as the ironcontent contained in the slag which comprises the sea water-immersionblocks.

(3) However, for partially recovering the metal by the magneticseparation, such grain iron does not always remain, but rather it isrecovered and removed, and large sized metal is probably left. On theother hand, the method (b) can arbitrarily select shapes and sizes ofmetallic iron to be added to the slag, and a desirable iron source suchas grain iron can be contained in the slag.

Therefore, for obtaining slags containing metallic iron or metalcontaining iron materials, it is most preferable to once remove allsubstantial parts in slag (except inevitably removable metals) by ametal removing treatment, and to add the metallic iron or metalcontaining iron materials as new additives.

In general, as later mentioned, the metal removing treatment is carriedout by the magnetic separation after pulverizing slags into grain orrough grain. Including slags of grain like or rough grain like statesper se, the slag having passed the metal removing treatment becomesinevitably grain or rough grain. Ordinarily, the slag passing the metalremoving treatment a has grain size of mm-order or smaller.

In the above metal removing treatment, metals in slags are desirablyremoved as much as possible, except inevitably removable metals.Normally, the iron content (metal) in slag after the metal removingtreatment is preferably less than 3 wt %. With respect to the slaghaving passed the metal removing treatment, such slags are obtainedwhich have the iron content of a desired amount containing the metalliciron such as grain iron and/or the metal containing iron material.

As the metallic iron or the metal containing iron material to be addedinto slag, the following is taken into consideration. One of them isthat, when molding the slag, the metallic iron or the metal containingiron material of large shapes do not hinder the molding. The other is toenlarge specific surface areas of such as the metallic iron contained inslag for heightening dissolution of the iron content from blocksimmersed in the sea water. From the above viewpoint, preferable arethose of small grain size and uniform scale, and from this, the grainiron is most desirable. As the grain iron, not only grain iron recoveredfrom slag but also other grain iron arbitrarily available may be used.

Depending on circumstances of sea water areas of the immersion block,there is a possibility of encountering problems of a shortage of oxygenin the sea water owing to an oxidation of the iron content in the slagor an excessive supply of iron content in the sea water. In order tosolve the above-mentioned problems, the slag to be used is subjected toa metal removing treatment and is used as raw material of a blockmaterial without adding metal iron or metal including iron material.

The slags generated in the iron-steel making process as mentioned abovecontain relatively much metal, though more or less, and the metals inslags are recovered at considerable degree by the metal recoveringtreatment. However since the slag content and the metal are mixed(entangled), the metal cannot be completely removed by a pulverizingtreatment of such degree as an ordinary metal recovering process, and soa considerable amount of metal remains in the slag after the metalrecovering process. Therefore, for sinking of a sea water block obtainedfrom slag having passed only a metal recovery, problems will arise withrespect to a shortage of oxygen in the sea water owing to the oxidationof iron content in slag or excessive supply of iron content into the seawater. Thus, for blocks to be applied to such sea areas, the slags to beraw material are those which have removed main metal by passing a metalremoving treatment.

As mentioned above, since the slag content and the metal are mixed inslag (entangled), it is necessary to remove the metal by magneticseparation under conditions of using pulverized slags into grain like orrough grain like. Including slags of grain or rough grain states per se,the slag having passed the metal removing treatment becomes inevitablygrain or rough grain. Ordinarily, the slag passing the metal removingtreatment has a grain size of mm-order or smaller (for example, 5 mm orlower).

Therefore, for the sea water-immersion blocks of the invention to beapplied in the sea area involved with the problems concerning theshortage of oxygen in the sea water owing to oxidation of the ironcontent in slag or the excessive supply of iron content in the seawater, the raw material is the slag shaped in grain and/or rough grainhaving passed the metal recovering treatment.

In the metal removing treatment, metals in slags are desirably removedas much as possible, except inevitably removable metals. Normally, theiron content (metal) in slag is preferably less than 3 wt %.

In the present embodiment, it is found that a main raw material is atleast one slag selected from a group of grain like slag, rough grainlike slag and small massive slag. Otherwise, the main material is a slagof grain like and/or rough grain like slag, which has passed the metalremoving treatment. This is consolidated (carbonation solidification) asthe binder of CaCO₃ or CaCO₃ and MgCO₃, and the massive blocks arewell-suited materials as blocks for algae planting places, buildingrocky beaches or fish gathering rocky places. At least the abovementioned slag includes such slags added with metallic iron and/or metalcontaining iron material.

It is an old technique to consolidate grains by reacting CaO and CO₂,that is, utilizing CaCO₃ produced by a carbonation reaction. If thegrain containing CaO is laid under an atmosphere of carbon dioxide,CaCO₃ is produced by the following formula, and a consolidatingphenomenon occurs as a binder of CaCO₃ among grains.CaO+CO₂→CaCO₃

Previously, as techniques making use of the carbonation reaction, thereare proposals of a method of making a raw material with a mixture ofwater and air-granulated slag in a steel-making process for makingsolidified products for buildings (e.g., Japanese Laid-Open Patent58-74559), or a method of making non-calcined pellets (e.g., JapaneseLaid-Open Patents 57-92143, 58-48642, and 58-133334). However theseprior art publications aim only at making hardened products ornon-calcined pellets having desired strength in a short period of time.These publications make no reference to block materials obtained byconsolidating, through a carbonation reaction, grain like, rough grainlike or small massive slags, otherwise the grain or rough grain likeslags passing a metal recovering treatment, and that the thus obtainedblocks are very useful materials as sea water-immersion blocks for algaeplanting places owing to properties thereof.

With respect to the grain containing MgO, if it is laid under anatmosphere of carbon dioxide, MgCO₃ is produced by the carbonationreaction and a consolidating reaction occurs as a binder of MgCO₃ amonggrains. MgCO₃ generated by a carbonation reaction of MgO is variouslymodified as an anhydrate, a hydrate (for example, a dihydrate, atrihydrate, a pentahydrate) hydroxide salt (basic magnesium carbonate),and a trihydrate of MgCO₃ is produced by the following formula.MgO+CO₂+3H₂O→MgCO₃.3H₂O

In general, the slag generated in the iron-steel making process containsa considerable amount of CaO (ordinarily, 20 to 60 wt. %), and the blockmaterials to be immersed in the sea according to the present inventionare those produced by changing, into CaCO₃, at least one slag selectedfrom the group of the grain like slag, the rough grain like slag and thesmall massive slag, otherwise CaO or Ca(OH)₂ modified from this CaO(including as needed CaO, Ca(OH)₂) contained in grain like slag and/orthe rough grain like slag, and consolidating to make massive the slaggrains (if containing the additives, grain or slag grain) with a binderof CaCO₃.

Major parts of slags contain MgO of a certain amount together with CaO,and the block materials to be immersed in the sea according to thepresent embodiment where such slag is the raw material, changes MgO orMg(OH)₂ modified from this MgO (including as needed MgO, Mg(OH)₂) intoMgCO₃ by the above mentioned carbonation reaction, and consolidating tomake massive the slag grains (if containing the additives, grain or slaggrain) with a binder of MgCO₃ and CaCO₃.

Incidentally, as mentioned above, MgCO₃ produced by the carbonationreaction of MgO is variously modified as an anhydrate, a hydrate or ahydroxide salt, and MgCO₃ contained as the binder in the seawater-immersion blocks of the invention is sufficient with any formedMgCO₃. For example, the hydrates of MgCO₃ are MgCO₃.2H₂O, MgCO₃.3H₂O orMgCO₃.5H₂O, and hydroxide salt (basic magnesium carbonate) isMgCO₃.Mg(OH)₂.3H₂O, 4MgCO₃.Mg(OH)₂.4H₂O, 4MgCO₃.Mg(OH)₂.5H₂O, or4MgCO₃.Mg(OH)₂.8H₂O. Further, MgCO₃ combines with other salts to formvarious double salts, and MgCO₃ existing as these double salts issufficient.

With respect to the slag generated in the iron-steel making process,parts or all of CaO or MgO contained therein are sometimes changed intoCa(OH)₂ or Mg(OH)₂ by water absorption as time passes or other causes,however this is no problem to the block to be utilized in the invention,and Ca(OH)₂ or Mg(OH)₂ are changed into CaCO₃ or MgCO₃ as the immersionblocks in the sea.

The immersion blocks in the sea have the following merits as blocks foralgae planting places, building rocky beaches or fish gathering rockyplaces.

(1) Major parts of CaO (or Ca(OH)₂ produced from CaO) contained in theslag is changed into CaCO₃, and so the pH of the sea water is preventedfrom increasing by CaO. On the other hand, the iron content (inparticular, metallic iron or metal containing iron material) of a properamount is contained in slag, and this iron content is dissolved, therebyto supply an iron content as a nutrient salt which is useful for rearingmarine algae in the sea water.

(2) At least one slag selected from the group of the grain like slag,the rough grain like slag and the small massive slag, otherwise themassive slag obtained by carbonation-solidifying the grain like slagand/or the rough grain like slag having passed the metal removingtreatment, have porous properties as a whole (surface and interior), sothat the marine algae easily attach to the surfaces of blocks. Inaddition, since the interior of the block is also porous, elementscontained in blocks useful for growing and accelerating of the algae(for example, later mentioned soluble silica or iron content) are easilydissolved. Therefore, those can effectively accelerate growing of themarine algae compared to the case of using massive slags per se forbuilding sea water-immersion blocks or fish gathering rocky places madeof concrete where the slag is an agglomerate.

In particular, for effectively accelerating the increase and living ofmarine algae on immersion blocks at places of building algae plantingplaces, the living of young algae should be accelerated on the blocksurfaces. In this regard, as the useful elements dissolving in the waterfrom immersion blocks effectively work if individuals of the marinealgae are near to blocks, they are very useful to the living of youngalgae.

(3) When using massive slags per se as immersion blocks, because ofrestraints of cooling methods or conditions of molten slags, dimensionsof slag are limited (ordinarily, about 800 mm at maximum), and it isdifficult to provide large massive blocks of regular sizes. On the otherhand, at least one slag selected from the group of the grain like slag,the rough grain like slag and the small massive slag (otherwise theblocks obtained by carbonation solidifying the grain like slag and therough grain like slag), can arbitrarily adjust the size by selectingshapes when carbonation-solidifying or selecting cut shapes after thecarbonation solidification. It is possible to easily obtain largemassive blocks particularly suited to algae planting places or fishgathering rocky places.

(4) It is preferable to use immersion blocks in the sea of optimumdensity (specific gravity) in response to conditions of sea bottom orcurrents. For example, when sinking blocks of large density to seabottoms such as piling of sludge, the blocks are immersed into thesludge and cannot serve as algae places or fish gathering places. Inthis regard, at least one slag selected from the group of the grain likeslag, the rough grain like slag and the small massive slag, otherwisethe blocks obtained carbonation solidifying the grain like slag and/orthe rough grain like slag having passed the metal removing treatment,can arbitrarily adjust the density by appropriately adjusting bulkdensity (compaction density).

(5) In the case of blocks for sinking in the sea obtained from the grainlike slag and/or rough grain like slag having passed the metal removingtreatment, since the main metal content is removed, if the blocks areapplied in such sea areas having problems regarding the shortage ofoxygen of the sea water or an excessive supply of the iron content,there occurs no problem of a shortage of oxygen in the sea water byoxidation of the metal or the excessive supply of the iron content bydissolution thereof. Further, the blocks for sinking in the sea obtainedfrom slag having removed the metal have relatively many componentsattributing to the carbonation solidification of the slag by an amountof removing the metal, and those are useful for securing strength.

The blocks for sinking in the sea of the present embodiment are producedby closely consolidating slags of small diameter with binders of CaCO₃or CaCO₃ and MgCO₃ produced by the carbonation reaction, and have enoughstrength. So, when transferring or sinking in the sea, those are notcracked or broken, even after having laid in the sea for a long periodof a year.

For providing suited compositions in response to conditions of sea areasto be applied, it is possible to contain various kinds of additives(grain like slag, rough grain like slag or small massive additives) intothe immersion blocks in the sea, together with at least one slagselected from the group of the grain like slag, the rough grain likeslag and the small massive slag, otherwise the blocks obtainedcarbonation solidifying the grain like slag and the rough grain likeslag having passed a metal removing treatment. As the additives,enumerated are such as grains or rough grains to be a soluble silicasource (soluble silica or materials containing soluble silica), grainlike or rough grain like to be an iron source (metallic iron, metalcontaining iron material, oxidized iron or oxidized iron containingmaterials), or CaO of grain like or rough grain like. For CaO containedas the additive in the immersion blocks in the sea, it is necessary toleave at least parts of CaO to be significantly added to CaO containedin the slag or the slag as non-reacted CaO after a carbonationsolidification.

The soluble silica or the iron source (iron or oxidized iron) containedin the immersion blocks is dissolved in the sea, thereby to usefullywork to sustain the living of marine algae. From the viewpoint of thedissolution in the seawater and the breeding of marine algae, themetallic iron or the metal containing iron material among the ironsources are particularly preferable. However, there are some caseswherein the seawater immersion blocks obtained from the grain like slagand/or rough grain like slag having passed a metal removing treatmentare applied in such sea areas having problems concerning the shortage ofoxygen in the sea water or excessive supply of the iron content. In thiscase, the metallic iron or the metals containing iron material are notadded.

When phosphorus is a cause of a red tide or sulfur is a cause of a bluetide are substantially contained in the sea bottom, CaO contained a bitin the immersion blocks absorbs phosphorus or sulfur. In the casewherein CaO is substantially contained in the block material asmentioned above, there is a problem of increasing the pH of theseawater, however, for absorbing phosphorus or sulfur, it is sufficientto contain CaO in a small amount to an extent of remaining after thecarbonation solidification.

As grains or rough grains to be the soluble silica source, included arethe soluble silica and/or the material containing the soluble silica ofthe grain or rough grain. As a material containing the soluble silica,fly ash or clinker ash may be used which are generated by coalcombustion such as in a thermal power station. The fly ash contains thesoluble silica in an amount of 45 to 75 wt. %, while the clinker ashcontains 50 to 65 wt. %.

The water granulated slag from a blast furnace also contains relativelymuch soluble silica, and if parts or all of the slag are rendered to bethe water granulated slag, for example, if a slag by steel making andthe water granulated slag are mixed, a similar effect is brought aboutto the case of adding the additive to be a soluble silica source.

As the grain or the rough grain to be the iron source, included are thegrains or the rough grain as the grain iron, the metallic iron, or themetal containing iron material, the grain like or rough grain likeoxidized iron and/or the oxidized iron containing material, and inparticular, cheaply available grain or rough grain are iron containingdusts generated in the iron-steel making process. The iron containingdust is generally a dust from iron making, and ordinarily containsoxidized iron of about 75% in terms of Fe. Mill scales also containsoxidized iron of about 70% in terms of Fe.

As mentioned above, when sinking blocks of large specific gravity to thesea bottom such as piling of sludge, the blocks are immersed into thesludge and cannot serve as algae places or fish gathering places.Therefore, with respect to the block material to be used to the seabottom of piled sludge, it is preferable that a slag of relatively smallspecific gravity is a main raw material, and specifically, it is usefulto use the water granulated slag of the small specific gravity ratherthan that of other slag as at least one part of the main raw material.

The block material of the present embodiment is relatively porous,thereby bringing about the above-mentioned effects. Percentage of voidsis not especially limited, however normally about 10 to 70% is thepreferable percentage of voids.

Explanation will now be provided for a method of making block materialsto be immersed in the sea.

FIG. 5 is one example showing the production flow of the inventivemethod, and FIG. 6 is one example showing the production procedureaccording to said flow. The slag generated in the iron-steel makingprocess is at first subjected to a metal recovery where a considerableamount of the metal content is removed from the slag. Ordinarily, inthis metal recovering process, the slag is pulverized into a grain sizeof cm-order or lower (for example, 5 cm or less) by such as a crusher tobe grain, rough grain or small massive slags, followed by the metalrecovery. The slag is sufficient with a grain size enabling recovery ofthe metal, and accordingly, if being relatively rough owing toproperties of the slag, those enabling to recover the metal arepulverized to a degree enabling to remove the metal.

In the above mentioned metal recovery, the metal content in the slagafter the recovering treatment may not be as low as a later mentionedmetal removing treatment, and the metal of a proper amount may be leftremaining. This is why the iron content in the slag in a proper amountis dissolved in the seawater, so that the iron content is supplied as anutrient salt in the seawater, and this is useful for rearing marinealgae. Thus, the metal content in slag is appropriately 3 wt. % or moreafter the recovering treatment.

There are some of slags brought in as stated where the slags arenaturally destroyed to grain sizes enabling to recover the metal(namely, the naturally destroyed states in grain, rough grain or smallmassive grain), and the pulverizing treatment as mentioned above is notnecessary therefor. For example, non-slagged CaO in the slag aftercooling and solidifying reacts with the water content in air, rainwateror sprinkled cooling water and generates Ca(OH)₂, and by this generationthe slag is expanded and destroyed, otherwise in a slag having abasicity (CaO/SiO₂) being near to 2, 2CaO.SiO₂(C₂S) is produced , andthis C₂S creates transforming expansion during cooling and the slag isdestroyed or crushed. The slags which are naturally destroyed by thesecauses to grain sizes enabling to recover the metal may be practicedwith the metal recovery.

Ordinarily, the metal recovering treatment is carried out by a magneticseparation of a magnetic separator (a method of removing the grain ironcontent from the slag by magnet), however no limitation is made thereto.For example, available is a gravity density method such as an airseparation making use of a difference in specific gravity between themetal content and the slag content.

The metal recovering treatment recovers the metal content in the slag.

The slag having passed the above mentioned metal recovery is at leastone slag selected from the group of the grain like slag, rough grainlike slag and the small massive slag, and is sent to a subsequentcarbonation solidification or a preparatory treatment. The raw slag issufficient with at least one of slags selected from the group of thegrain like slag, rough grain like slag and the small massive slag, andit is not a necessary condition to pass the metal recovering procedure.

Many slags which have passed the metal recovering process, contain thegrain like slags or rough grain like slags more than a certain ratio,though being more or less. Therefore, even if the slag contains smallmassive slag grains of relatively large diameter, there is scarcely thepossibility of causing hindrances in carbonation-solidifying the slaggrains into a state having a predetermined strength, since grain orrough grain like slags pack spaces among the small massive slag grains.However, when the slag is composed of only substantially small massiveslag grains, or when the ratio of the small massive slag grain occurringin the slag is relatively high, since the contacting areas of the slaggrains are small, there might be a probability of causing hindrances incarbonation-solidifying the slag grains into a state having apredetermined strength. Therefore, it is preferable to adjust the grainsize by increasing the ratio of the grain like slags or rough grain likeslags.

The iron content in slag may be utilized as it is without recoveringparts or all of the metal contained per se in the slag. However, inorder to optionally control, as mentioned above, the iron contentcontained in the slag, in order to arbitrarily select shapes or sizesthereof, and in order to contain a preferable iron source such as grainiron, it is preferable to add the metallic iron and/or metal containingiron materials as additives, after removing all substantial parts in theslag (except inevitably non-removable metals) by a metal removingtreatment.

The metal removing treatment is generally performed by pulverizing theslag by a pulverizer until obtaining mm-order or smaller (for example5mm or smaller) particles. The slag is sufficient with such sizesenabling to remove the metal and, accordingly, depending on theproperties of the slags, those enabling to remove the metal in spite ofbeing a relatively rough grain may be pulverized to sizes enabling toremove the metal. Slags being already grain or rough grain by naturalpulverization do not often need a pulverizing treatment. In the metalremoving treatment, except inevitably remaining metal content, the metalis preferably removed as much as possible. The metal content in slag isless than 3 wt. % after the removing treatment.

Ordinarily, the metal recovering treatment is carried out by a magneticseparation in a magnetic separator (a method of removing the grain ironcontent from the slag by a magnet), however no limitation is madethereto. For example, available is a gravity separation method such asan air separation making use of the difference in specific gravitybetween the metal content and the slag content.

To the slag having passed the metal removing treatment, the metalliciron as grain iron and/or the metal containing iron materials are addedin the appropriate amounts for obtaining slag having an iron content ofa desired amount containing metallic iron or the metal containing ironmaterial. This slag is sent to the subsequent carbonation solidificationor the preparatory treatment. As the metallic iron or the metalcontaining iron material to be added into the slag, the grain iron isoptimum. As the grain iron, not only grain iron recovered from the slag,but also arbitrary grain iron from others can be used.

FIG. 7 is one example of the production flow of producing the blockmaterials to be immersed in the sea without adding metallic iron or themetal containing iron material after performing the metal removingtreatment. FIG. 8 is one example showing the production procedureaccording to said flow. The slag generated in the iron-steel makingprocess is at first subjected to the metal removing treatment forremoving the main metal content. In general, the slag content and themetal in slag are closely entwined, and for the metal removingtreatment, the slag should be pulverized in grain size or rough grain,and normally the slag is pulverized by the pulverizer to mm-order orlower (e.g., 5 mm or less). The slag is sufficient with such sizesenabling the removal of the metal and, accordingly, depending onproperties of slags, those enabling the removal of the metal in spite ofbeing relatively rough grain may be pulverized to sizes enabling toremove the metal.

In the metal removing treatment, except inevitably remaining metalcontent, the metal should be preferably removed as much as possible, andthe metal content in slag is less than 3 wt. % after the recoveringtreatment.

As mentioned above, there are some slags brought in as stated where theslags are naturally destroyed to grain sizes enabling the recovery ofthe metal, and the pulverizing treatment as mentioned above is notnecessary therefor. The causes of the natural destruction are asmentioned above, and the slags which are naturally destroyed by thesecauses to grain sizes enabling the recovery of the metal may bepracticed with the metal recovery.

Ordinarily, the metal recovering treatment is carried out by a magneticseparation of the magnetic separator (a method of removing the grainiron content from the slag by magnet), however no limitation is madethereto. For example, available is a gravity separation method such as awind separation making use of a difference in specific gravity betweenthe metal content and the slag content.

The metal content in the slag is removed by the metal removingtreatment.

The slag having passed the above mentioned metal removal is grain likeslag and/or rough slag, and is sent to the subsequent carbonationsolidification or the preparatory treatment thereof.

To at least one slag selected from the group of the grain like slag, therough grain like slag and the small massive slag, otherwise the grainlike slag and/or the rough grain like slag having passed the metalremoving treatment, the additives are added if necessary. When CaO orMgO necessary for the carbonation reaction are insufficient in the slag,one kind or more selected from CaO, Ca(OH)₂, MgO and Mg(OH)₂ are addedif required and mixed with the slag. As the additives, enumerated aresuch as grains or rough grains to be a soluble silica source (solublesilica or materials containing soluble silica), grains or rough grainsto be an iron source (metallic iron, metal containing iron material, anoxidized iron or oxidized iron containing materials), or CaO. Thespecific examples are as mentioned above.

Among them, the soluble silica or the iron source (metallic iron oroxidized iron) is dissolved in the sea, thereby to usefully work tosustain the living of the marine algae. From the viewpoint of thedissolution in the sea water and to sustain the living of the marinealgae, the metallic iron or the metal containing iron material among theiron sources are particularly preferable. However, in the case of blocksfor sinking in the sea obtained from the grain like slag and/or roughgrain like slag having passed the metal removing treatment, if theblocks are applied in such sea areas having problems regarding theshortage of oxygen in the sea water or an excessive supply of the ironcontent, the metallic iron or the metal containing iron material are notadded.

Mixture of the slag and the additional raw materials such as theadditives or CaO may depend on arbitrary methods, for example, a methodof mixing the additional raw material and the slag exhaust from themetal recovering facility or the metal removing facility in a hopper, amethod of adding the additional raw material to the slag having passedthe metal removing treatment to mix in the metal recovering facility orthe metal removing facility, a method of mixing by a heavy machinery asa shovel, or a method of mixing by a concrete mixer car (concreteagitator).

In this stage, the water content in slag may be adjusted as needed. Theadjustment of water content will be referred to in detail later.

The slag which has been added with the additives as needed, mixed andadjusted in the water content is piled for carbonation solidification orfilled up in optional spaces.

Herein, for piling the slags, it is sufficient to pile in the open air.However, it is preferable for the blown carbon dioxide to flow all overthe piled mountains, and it is more preferable to cover the piledmountains with sheets for preventing the slag from scattering or fadingby rainwater.

For piling or packing with the slag, available are pits encircling threecorners with partitioning walls, frames or containers encircling fourcorners with the partitioning walls. When piling or packing with theslag within the pit, it is preferable to cover the piled or filled-upmountains with the sheets similarly to the open-air freighting. Further,when using a frame or container, it is desirable to cover the slagpacked bed with the sheet or provide a cover body. FIGS. 6 and 8 showstates where the packed bed A is formed within the frame.

The piling amount or the filling amount of the slag are not limited, andsaid amounts of several tons or several hundred tons are sufficient, orsaid amount corresponding to one piece of the block material or severalpieces are enough. Thus the amount is optional. Although the piling orfilling amount is much, if the piled mountain or the packed bed afterthe carbonation solidification are pulverized by heavy machinery,massive block materials can be cut out, and such cut-out massive blockshave merits of irregularity fractures for catching marine algae. Fromthe viewpoint of productivity or functions as blocks for algae plantingplaces or fish gathering rocky places, it is preferable that the slagpiling or packing amounts are much to a certain degree.

The bulk density (compaction density) of the slag pile or layer ispreferably adjusted in response to a density of block to be produced.Namely, the immersion block in the sea should be adjusted with respectto the density in response to conditions of the sea bottom. For example,in the case where the sea bottom is muddy or sludgy, blocks ofrelatively low density should be used so that the blocks are notimmersed into the mud or sludge. On the other hand, in the case wherethe sea bottom is a reef, etc., blocks of relatively high density shouldbe used so that the blocks are not carried away. Since the adherence ofmarine algae, the living degree thereof or dissolution of usefulcomponents from the interior of blocks are varied by the porosity(vacancy) of the block materials, it is often preferable to adjust theporosity of the blocks in response to conditions of the sea areas wherethe blocks are used.

The density of blocks to be produced by the method of the presentembodiment depends on the bulk density (compaction density) of the piledmountain or packed bed, and so, it is possible to adjust the tighteningdegree of the piled mountain or packed bed, and by adjusting the bulkdensity, the density of block can be easily adjusted.

The tightening degree of the slag piled mountain or packed bed isoptional, however ordinarily, the bulk specific gravity/true specificgravity ranges from 0.3 to 0.9, that is, the tightening is carried outto a degree that the vacancy within the piled mountain or packed bed is70 to 10%.

The tightening may depend on a method of tightening the upper part ofthe piled mountain or packed bed or a method of giving vibration totighten the piled mountain or packed bed. By adjusting the tighteningdegree, the density of the piled mountain or packed bed is adjusted.When producing the blocks of low density, the tightening is notperformed, and the carbonation solidification is practiced as piled orfilled up.

As actually tightening method, when tightening the piled mountain orpacked bed within the above mentioned pit or molding frame, weighinglines for showing a target volume are marked on the interior of the pit,molding frame or container, and the slag whose weight is known is laidtherein, and the tightening is continued until the upper face of thepiled mountain or packed bed comes to the weighing line.

After completing the adjustment of the bulk specific gravity of thepiled mountain or packed bed of slag, the carbonation reaction is causedin the piled mountain or packed bed under the existence of carbondioxide for carbonation-solidifying the slag. Specifically, the carbondioxide or the carbon dioxide containing gas is blown into the piledmountain or packed bed of slag, otherwise the piled mountain or packedbed is laid under an atmosphere of carbon dioxide or a carbon dioxidecontaining gas for practicing the carbonation solidification of slag.

The above blowing manner is not especially limited, however it is mosteffective to equip a gas blowing instrument at the bottom of the piledmountain or packed bed and blow the gas through this instrument.Actually, gas supplying pipes or hoses are disposed at an appropriatepitch (e.g., 30 to 300 mm×40 to 400 mm) in the bottom of the mountain orlayer (if using the pits, molding frames or containers, in beds thereof)for blowing the carbon dioxide or the carbon dioxide containing gas.

Further, as the manner for laying the mountain or layer in theatmosphere of the carbon dioxide or the carbon dioxide containing gas,the mountain or layer are laid in air-tight spaces (including thecontainer), into which the carbon dioxide or the carbon dioxidecontaining gas is supplied by an arbitrary embodiment.

As the carbon dioxide containing gas to be employed, the suited examplesare as follows. That is to say, an exhaust gas (normally, CO₂: around25%) from a limestone baking plant of an integrated iron making work oran exhaust gas form a reheating furnace(normally, CO₂: around 6.5%) canbe used. However no limitation is made thereto. If the concentration ofcarbon dioxide in the carbon dioxide containing gas is too low, aproblem occurs that the treating efficiency is decreased, however noother problem appears. Thus, the concentration of carbon dioxide is notlimited, however for efficient treating, it is preferably 3% or higher.

The gas blowing amount of the carbon dioxide or the carbon dioxidecontaining gas is not limited either and, as an ordinary standard, it isgood to use a gas blowing amount of about 0.004 to 0.5 m³/min·t. Inaddition, there is no limitation especially required for the gas blowingtime (carbonation treating time) and, as a standard, it is desirable toblow the gas until the blowing amount of carbon dioxide (CO₂) reaches 3%or more of the weight of the slag, that is, until carbon dioxide (CO₂)of 15 m³ or more per 1 ton of a material in terms of the gas amount issupplied.

The carbon dioxide or the carbon dioxide containing gas to be blown intothe piled mountain or packed bed of slag is sufficient at roomtemperature and, if the gas exceeds room temperature, this is better forreactivity An upper limit of the gas temperature is a temperature fordecomposing CaCO₃ into CaO and CO₂ or MgCO₃ into MgO and CO₂, and whenusing gas at a high temperature, gas at a temperature of not bringingabout such decompositions should be used. An optimum temperature foractual operation is necessarily determined by taking conditions of thewater content or other conditions into consideration.

For carbonation-solidifying the slag by utilizing the reaction of CaO,MgO and carbon dioxide, a water content is necessary, and the optimumwater content is varied according to the grains of slags, however it issuitable to have about a 3 to 10% water content rate in slag immediatelybefore starting the carbonation treatment. This is because thecarbonation reaction is accelerated by dissolving CaO, MgO and carbondioxide in the water. Therefor, it is preferable to adjust the watercontent in slag to be an optimum value so as to cause the carbonationreaction under the existence of carbon dioxide. If the water content inslag is too low, desirably water is added to the slag in the mixingcourses of FIGS. 5 and 7 for adjusting the water content for heighteningthe amount of water contained in slag. If the carbon dioxide or thecarbon dioxide containing gas is once blown into the water to saturateH₂O, followed by blowing it into the piled mountain or packed bed, theslag is prevented from being dried to accelerate the carbonationreaction. Further, it is sufficient to adjust the water content inmixture to be a value at which a compression strength of a massivesubstance is at a maximum after the carbonation treatment. This value ofthe water content is obtained as follows.

(a) A raw slag of more than 3 standard is prepared, where a water of anoptional amount of more than a water absorption rate of the raw slaggrain is added to 100 wt parts of the raw slag. The above mentionedwater absorption rate is that of a fine aggregate or coarse aggregatespecified by JIS A1109 or A 1110.

(b) Respective raw slag is charged in the molding frame so that theporosity under the drying condition is kept to be constant andhomogeneous, and the charged layers are formed.

(c) The charged layer is blown with carbon dioxide gas humidified at 10to 40° C. at a determined amount for practicing carbonation curing for afixed time so as to solidify the raw slag.

(d) The compression strength of the solidified slag is measured forobtaining a maximum value thereof. The value of the water contentcorresponding to the maximum value is the optimum water content.

By supplying the carbon dioxide or the carbon dioxide containing gasinto the piled mountain or the charged layer of the slag, CaCO₃ or MgCO₃is produced by the reaction between CaO (or Ca(OH)₂) or MgO (or Mg(OH)₂)and the carbon dioxide CaCO₃ or CaCO₃ and MgCO₃ are rendered to bebinders for solidifying the slag grain (if the additive is mixed, theslag grain and additive grain).

After completion of the carbonation solidification, the piled mountainor the charged layer are broken into required sizes by heavy machinery,and cut out into massive block materials to be immersed in the sea.Ordinarily, the blocks are cut out into sizes of 80 to 1500 mm. By thispulverization when cutting out, the blocks have fractures ofirregularities for easily catching marine algae.

In the method of the present embodiment, by a sufficient small volume ofcharged layer, it can be utilized as the block material as it is,without cutting out.

The production method of this embodiment has the following merits.

(1) Since the carbonation solidification is practiced under theconditions of piling the slag in a mountain or a charging layer, thedensity of the immersion block in the sea can be easily adjusted byadjusting the tightening degree of the piled mountain or the chargedlayer for adjusting the bulk specific gravity. As mentioned above, theblocks should be adjusted in the density or the porosity in response toconditions of the sea bottom or current, and as the production method,it is a big merit that the adjustment can be arbitrarily and easilycarried out. A conventionally known technique is to carbonation-solidifygranulates, which is however difficult to adjust the density ofnon-treated materials in wide ranges.

(2) The method of this embodiment carries out the carbonationsolidification under the condition of piling or charging the slag in amountain or a layer, breaks the carbonation-solidified mountain or layerfor cutting out the massive blocks into desired sizes or utilizes thecharged-layer as blocks as they are. So, by appropriately selectingsizes of the cut-out blocks or the charged layer, the blocks of optionalsizes (for example, 80 to 1500 mm) can be obtained, and large massiveblocks especially suited to algae planting places or fish gatheringrocky places can be easily obtained. In the prior art ofcarbonation-solidifying granulated pellets, sizes of obtained massiveproducts are 30 to 50 mm at the most, besides inevitably producingmassive ones of a small size. Thus, as the production method of thesea-immersion blocks, it is a big advantage that large massive blockscan be obtained.

(3) After the carbonation solidification, the piled mountain or thecharged layer are broken by heavy machinery, and cut out into massiveblock materials, so that the blocks have surfaces (fractures) ofirregularities for easily catching marine algae.

The block materials can exhibit excellent characteristic when using themfor algae planting places, building beaches, or fish gathering rockyplaces, and of course they can be used for other purposes, for example,as blocks for sea bottom mound, improving or purifying qualities of thesea bottom. Also when the blocks are used for such purposes, theexcellent effects as mentioned above are exhibited for living marinealgae.

EXAMPLE 3

A converter slag powder (containing small massive slags produced by themetal recovery, iron content: 12 wt. %) of a maximum diameter about 30mm, and a grain size of 5 mm or smaller and being about 70 wt. %, waspiled 1.5 m in a pit of 4 m width×6 m depth, and moderately tightened.Then the pit was closed and blown with carbon dioxide 50 Nm³/hr for 3days so as to solidify the slag. The carbonation-solidified slag wasbroken and divided by heavy machinery to produce massive block materialsof about 1.0 to 1.5 m for algae planting places.

As a comparative example, mortar was poured into the molding frame of1.5 m×1.5 m×1.5 m, and the solidified concrete block was divided intotwo by a breaker (rock drill) to produce blocks having fractured facesfor an algae planting place.

A sea bottom, which was 4 m deep and near a natural algae plantingplace, was selected as a place for building a testing algae plantingplace. 15 pieces of the block materials of the above example and 20pieces of blocks of the comparative example were immersed in a scope ofdiameter being about 10 m. The blocks of the comparative example wereimmersed turning the fractured faces upward. A period of the seasons forsinking blocks was selected just before spending spores from the naturalmarine algae planting place in order that sedimentary substances did notcover the block surfaces before adhered spores thereto.

As a result of investigating the places of sinking blocks after aboutone year, it was confirmed that marine algae adhered to all the blocksand lived. The living amount of algae was surveyed by an investigationof a crop estimate by unit acreage sampling, and it was confirmed thatthe humid weight of the blocks of the comparative example was 956 g/m²,while the humid weight of the blocks of the example was 1121 g/m², andthat the blocks of the invention were better in adhering rate and forsustaining the living properties of algae.

EXAMPLE 4

A converter slag grain like (having passed the metal recovery, ironcontent: 2 wt. %) of grain size being 3 mm or smaller, was piled 1.5 min a pit of 4 m width×6 m depth, and moderately tightened. Then the pitwas closed and blown with carbon dioxide 50 Nm³/hr for 3 days so as tosolidify the slag. The carbonation-solidified slag was broken anddivided by heavy machinery to produce the massive block materials ofabout 1.0 to 1.5 m for algae planting places.

As a comparative example, mortar was poured into the molding frame of1.5 m×1.5 m×1.5 m, and the solidified concrete block was divided intotwo by a breaker (rock drill) to produce blocks having fractured facesfor the algae planting place.

A sea bottom of 4 m deep near a natural algae planting place wasselected as a place for building a testing algae planting place. 15pieces of the block materials of the above example and 20 pieces ofblocks of the comparative example were immersed in a scope of diameterbeing about 10 m. The blocks of the comparative example were immersedturning the fractured faces upward. A period of the seasons for sinkingblocks was selected just before spending spores from the natural marinealgae planting place in order that sedimentary substances did not coverthe block surfaces before spores adhered thereto.

As a result of investigating the places of sinking after about one year,it was confirmed that marine algae adhered to all the blocks and lived.The living amount of algae was surveyed by an investigation of a cropestimate by unit acreage sampling, and it was confirmed that the humidweight of the blocks of the comparative example was 579 g/m², while thehumid weight of the blocks of the example was 695 g/m², and that theblocks of the invention were better in adhering rate and sustaining theliving properties of algae.

According to the above mentioned present embodiments, neither anincrease of the pH in the sea water or a shortage in oxygen areencountered, and when using them for algae planting places, buildingbeaches, or fish gathering rocky places, the block materials can exhibitan excellent performance also for sustaining the living of marine algae,and in addition, it is possible to offer the block materials for sinkingin the sea which are adjustable in size and density.

Further, according to the sea water immersion block of the inventionusing raw slag having passed a metal recovering treatment, in additionto the above mentioned effects, in the sea areas necessary to suppressthe shortage of oxygen in sea water owing to the oxidation of ironcontent in slag or the excessive supply of iron content into the seawater, it is possible to effectively suppress the shortage of oxygen inthe sea water owing to the oxidation of iron content in slag or theexcessive supply of iron content into the sea water.

In particular, in the production method of the present embodiments, asthe carbonation solidification is carried out under the conditions ofpiling or packing the slags, it is possible to produce sea waterimmersion blocks of optional density and sizes easily and at a low costby adjusting the degree of tightening of the piled mountain or thecharged layer, or appropriately selecting sizes of thecarbonation-solidified blocks to be cut out.

There are some slags which have a property to be floured by atransforming expansion of γ-dicalcium silicate generated when cooling,or expansion caused by hydration of free CaO. Conventionally, suchfloured slag has not been used other than being partially utilized asraw materials for cements, and major parts were wasted. However in thepresent embodiments, floured slag can be utilized as a raw material.Further, with respect to slags (for example, dephosphorized slag ordesilicated slag) having difficulties in usefully using them as cementraw materials owing to restraints in compositions, the inventive methodcan use them as the raw material. Thus, this is a very profitableinvention also in a regard of usefully using slags generated in theiron-steel making process.

River Water Immersion Block and Production Method Thereof

The inventors made experiments and investigations, and as a result, theyfound the following facts.

(1) Grain like slags, rough grain like slags or small massive slags, inparticular such slags moderately containing iron content areconsolidated with a binder of CaCO₃ or CaCO₃ and MgCO₃ produced by acarbonation reaction, and the thus consolidated massive slag is used asriver immersion blocks. It was found that such blocks exhibit, when usedas sinking blocks, excellent effects in forming spaces for living fishesor the rearing of water living plants as algae without increasing the pHof the river water, or to above all display particularly excellenteffects in moving of other water living creatures than fishes or rearingof water living plants, when sinking or laying blocks to artificiallystructural parts or artificial river beds such as fish ways to beequipped to dams or barrages of rivers.

(2) On the other hand, for a river-flowing area which necessitatescontrolling the shortage of oxygen in the river water owing to oxidationof iron content or excessive supply of iron content into the riverwater, the grain like or rough grain like slags having passed the metalremoving treatment are consolidated with a binder of CaCO₃ or CaCO₃ andMgCO₃ produced by carbonation reaction, and the thus consolidatedmassive slag is used as river immersion blocks, thereby displayingexcellent effects in the rearing of algae without causing a shortage ofoxygen in the river water owing to the oxidation of iron content orexcessive supply of iron content into the river water or increasing thepH of the river water.

(3) For obtaining the massive immersion blocks in the river water asmentioned above, such a production method is useful which consolidatesthe above mentioned slags by piling or packing at a desired density thegrain like slag, the rough grain like slag or the small massive slag,otherwise the grain like or rough grain like slag having passed a metalremoving treatment, and by causing the carbonation reaction in the piledmountain or packed bed under the existence of carbon dioxide. Accordingto this production method, it is possible to produce blocks of arbitrarydensity and size in response to conditions of river beds orwater-flowing to be applied with blocks, and to produce blocks ofarbitrary density and sizes in response to purposes for river beds orfish ways at low cost.

The present embodiment is characterized as follows.

(1) The embodiment is concerned with immersion blocks in the rivers of amain raw material being a slag produced in the iron-steel makingprocess, and is characterized by a consolidating the slag with a binderof CaCO₃ produced by carbonation reaction, and making the slag massive.This slag is at least one selected from the group of the grain likeslag, the rough grain like slag and the small massive slag. The presentslag is sufficient with grain like or rough grain like slag havingpassed a metal removing treatment.

(2) The embodiment is concerned with immersion blocks in the rivers of amain raw material being a slag generated in the iron-steel makingprocess, and is characterized by consolidating the slag with a binder ofCaCO₃ and MgCO₃ produced by a carbonation reaction, and making the slagmassive. The embodiment includes a case where MgCO₃ exists as a hydrate,hydroxide salt or double salt. This slag is at least one selected fromthe group of the grain like slag, the rough grain like slag and thesmall massive slag. The present slag is sufficient with grain like orrough grain like slag having passed a metal removing treatment.

(3) The embodiment is concerned with immersion blocks in the rivers ofmain raw materials being a slag generated in the iron-steel makingprocess, grain like additives and/or rough grain additives, and ischaracterized by consolidating a mixture of the slag and the additiveswith a binder of CaCO₃ produced by a carbonation reaction, and makingthe slag massive. This slag is at least one selected from the group ofthe grain like slag, the rough grain like slag and the small massiveslag. The present slag is sufficient with grain like or rough grain likeslag having passed a metal removing treatment.

(4) The embodiment is concerned with immersion blocks in the rivers ofmain raw materials being a slag generated in the iron-steel makingprocess, grain like additives and/or rough grain additives, ischaracterized by consolidating a mixture of the slag and the additiveswith a binder of CaCO₃ and MgCO₃ produced by a carbonation reaction, andmaking the slag massive. The embodiment includes a case where MgCO₃exists as a hydrate, hydroxide salt or double salt. This slag is atleast one selected from the group of the grain like slag, the roughgrain like slag and the small massive slag. The present slag issufficient with grain like or rough grain like slag having passed ametal removing treatment.

(5) A method of making immersion blocks in the river water ischaracterized in that the slag generated in the iron-steel makingprocess is, as needed, mixed with one kind or more selected from CaO,Ca(OH)₂, MgO and Mg(OH)₂, and the slag is piled, or the packed bed isformed in an arbitrary space, and is caused with the carbonationreaction under the existence of carbon dioxide so as to consolidate theslag for providing blocks of the massive slag. This slag is at least oneselected from the group of the grain like slag, the rough grain likeslag and the small massive slag. The present slag is sufficient withgrain like or rough grain like slag having passed a metal removingtreatment.

(6) A method of making immersion blocks in the river water ischaracterized in that the slag generated in the iron-steel makingprocess is mixed with grain like additives and/or rough grain additivesand is, as needed, mixed with one kind or more selected from CaO,Ca(OH)₂, MgO and Mg(OH)₂, and the slag is piled or the packed bed isformed in an arbitrary space, and is caused with the carbonationreaction under the existence of carbon dioxide so as to consolidate theslag for providing blocks of the massive slag. This slag is at least oneselected from the group of the grain like slag, the rough grain likeslag and the small massive slag. The present slag is sufficient withgrain like or rough grain like slag having passed a metal removingtreatment.

The present embodiment is concerned with the immersion blocks in theriver water of a main raw material being a slag generated in theiron-steel making process. As the slag generated in the iron-steelmaking process, there may be enumerated slags from blast furnaces suchas a slowly cooled slag or a water granulated slag therefrom; slags fromthe iron-steel making process such as dephosphorized slag, desulfurizedslag, desiliconized slag, decarburized slag or casting slag generated inpre-treatments, a converter or casting; slags from iron ore reduction;or slags from electric furnaces. However, no limit is provided to them.Slags mixed with two kinds or more of slags may be used.

The slags generated in the iron-steel making process as mentioned abovecontain relatively much metal (iron content as grain iron) though moreor less (ordinarily, around several wt. % to 30 wt. %), and metals inslags are pulverized to recover for recycling the iron content to theiron-steel making process. Accordingly, including the grain like, roughgrain like or small massive slags, the slags having passed a metalrecovering process are necessarily the grain like, rough grain like orsmall massive slags. Ordinarily, grain sizes of the slag having passedthe metal recovering process are at cm-order or less (for example, 5 cmor less).

The present embodiment employs at least one of these grain like, roughgrain like or massive slags for rivers-immersion blocks.

The slag to be employed in the invention is sufficient with at least oneof the grain like, rough grain like or massive slags, and it is not anecessary condition to pass a metal recovery treatment.

When these slags are rendered to be raw materials of the river immersionblocks, the iron containing amount is not required to be low as the casewhere a slag having passed a metal removing treatment is rendered to bea raw material of a block. Rather, it is better that the iron content ofa proper amount (particularly, metallic iron or alloyed iron materialsuch as grain iron) is contained in slag. This is why the iron contentcontained in the slag in a proper amount is dissolved in river water, sothat the iron content is supplied as a nutrient salt in river water, andthis usefully works for rearing marine algae. Thus, the iron content inslag is appropriately 3 wt % or more.

Depending on circumstances of river areas to be immersed with blocks, incases of problems concerning the shortage of oxygen in the river waterowing to the oxidation of iron content in slag or the excessive supplyof iron content into the river water, the slag to be used is subjectedto a metal removing treatment and is used as a raw material of a blockmaterial without adding metal iron or the metal including iron material.

The slags generated in the iron-steel making process as mentioned abovecontain relatively much metal though more or less, and the metals inslags are recovered at considerable degree by the metal recoveringtreatment. However since the slag content and the metal are mixed asbeing entwined, the metal cannot be completely removed by a pulverizingtreatment of such degree as an ordinary metal recovering process, and soa considerable amount of metal remains in the slag after the metalrecovering process. Therefore, if sinking in the river blocks obtainedfrom the slag having passed only a metal recovery, problems will ariseconcerning the shortage of oxygen in the river water owing to theoxidation of iron content in slag or the excessive supply of ironcontent into the river water. Thus, for blocks to be applied to suchriver areas, the slags to be raw material are those which have removedmain metal by passing a metal removing treatment.

Since the slag content and the metal are mixed in slag as beingentwined, it is necessary to remove the metal (by a magnetic separation)under conditions of having pulverized slags into grain or rough grain.Including slags of grain or rough grain states per se, the slag havingpassed a metal removing treatment becomes inevitably grain or roughgrain. Ordinarily, a slag passing the metal removing treatment has agrain size of mm-order or less (for example, 5 mm or lower).

Therefore, for the river immersion blocks of the invention to be appliedin the river areas involved with the problems concerning the shortage ofoxygen in the river water owing to the oxidation of iron content in slagor the excessive supply of iron content into the river water, the rawmaterial is the slag shaped in grain and/or rough grain having passed ametal recovering treatment.

In the metal removing treatment, metals in slags are desirably removedas much as possible, except inevitably removable metals. Normally, theiron content (metal) in slag is preferably less than 3 wt. %.

In the present embodiment, it was found that the main raw material is atleast one slag selected from a group of grain like slag, rough grainlike slag and small massive slag, or the slag of grain and/or roughgrain having passed a metal removing treatment, and this is consolidated(carbonation solidification) as a binder of CaCO₃ or CaCO₃ and MgCO₃,and the massive blocks are very suited materials as blocks for sinkingto river beds, above all as artificially structural parts such as fishways or artificial river beds.

In general, the slag generated in the iron-steel making process containsa considerable amount of CaO (ordinarily, 20 to 60 wt. %), and the blockmaterials to be immersed in rivers according to the present inventionare those produced by changing, into CaCO₃, at least one slag selectedfrom the group of the grain like slag, the rough grain like slag and thesmall massive slag, otherwise CaO or Ca(OH)₂ modified from this CaO(including as needed CaO, Ca(OH)₂) contained in grain like slag and/orthe rough grain like slag, and consolidating to make massive the slaggrains (if containing the additives, grain or slag grain) with thebinder of CaCO₃.

Major parts of slags contain a certain amount of MgO together with CaO,and the block materials to be immersed in rivers according to thepresent embodiment where such slag is the raw material, changes MgO orMg(OH)₂ modified from this MgO (including as needed MgO, Mg(OH)₂) intoMgCO₃ by the above mentioned carbonation reaction, and consolidating tomake massive the slag grains (if containing the additives, grain or slaggrain) with a binder of MgCO₃ and CaCO₃.

With respect to the slag generated in the iron-steel making process,parts or all of CaO or MgO contained therein are sometimes changed intoCa(OH)₂ or Mg (OH)₂ by water absorption as time passes or other causes,however this is no problem for the block to be utilized in theinvention, and Ca(OH)₂ or Mg(OH)₂ are changed into CaCO₃ or MgCO₃ asimmersion blocks in rivers.

The river immersion blocks of the present embodiment are used as riverbeds or fish ways. The embodiment of installing blocks in the water isarbitrary as not only merely sinking but also fixing them to structuralparts.

The river immersion block materials of the present embodiment areparticularly suited as immersion blocks or laid to the artificiallystructural parts or artificial river beds as blocks for fish ways, andthe blocks for the fish way are laid or fixedly laid to the bottom ofthe fish way. Other than the fish way, the blocks may be fixedly laid tooptional structural parts such as the upper face of an artificiallystructural part where the water flows (for example, moderately obliqueface of the artificially structural part composing part or all of thehead-neck of a barrage) or a fixedly structured artificial river bed(for example, river beds constructed by block tightening or rockwork).

The embodiment (sizes or shapes) for using the river immersion blocks isoptional, and the sizes may be selected in response to usage from ordersof 1000 mm or larger to orders of several ten mm. When fixedly layingthe blocks to the fish ways, other artificially structural parts orartificial river beds, in order that an construction is easily carriedout, and as cases may be, the blocks are fixedly laid only withrockworks, it is desirable to use the blocks in a block, panel, tile orsimilar shape (fixedly formed material). Also in the fish ways, it issufficient to use the blocks in an embodiment of simply sinking themassive blocks of a non-fixed form on the bottom thereof.

FIGS. 9(a) to (c) show structural examples when the blocks of theinvention are immersed or laid on the artificially structural part orthe artificial river bed of such as fish ways, in which (a) is anexample where the block materials 40 a in block or panel shape arefixedly laid on the fish way of oblique road system. For fixing theblocks 40 a, mortar may be used as needed. In this example, the blocksof the bottom have fractures 40 (cracked or ruptured faces) Thefractures 40 are cracked or ruptured faces formed when the blocksprovided by the carbonation solidification are cracked or ruptured, andas those are more irregular than as-carbonation solidified faces, theyare effective for water living creatures to move. FIG. 9(b) is anexample of sinking the massive blocks 40 b non-fixedly on the bottoms(respective steps) of the stepwise fish way. FIG. 9(c) is an examplesinking the massive blocks 40 c of block or panel shape fixedly on theartificially structural parts or the artificial river bed other than thefish way. As the artificially structural part other than the fish wayapplicable with such structure, for example, the moderately oblique facecomposing the head-neck of such as barrages may be listed up.

The river immersion block have merits as follows as block materials tobe immersed or laid on the river bed.

(1) Major parts of CaO (or Ca(OH)₂ produced from CaO) is changed intoCaCO₃, and so it is possible to prevent algae from delaying of adheringor living by an increase of pH of the river water or around the blockmaterials. In general, the pH of natural blocks (limestone) is around9.3 and the pH of concrete is around 12 to 12.5, and the river immersionblock of the invention can be at a pH 10 or lower as a natural block bya neutralizing reaction at production.

(2) The massive slag obtained by carbonation-solidifying the grain likeslag and/or the rough grain like slag have porous properties as a whole(surface and interior), so that such as algae are easily attach thesurfaces of blocks. Besides, since the interior of block is also porous,elements contained in blocks useful to growing and accelerating of thealgae are easily dissolved, and the growth of algae is good.

(3) When using massive slags per se as immersion blocks, because ofrestraints of cooling methods or conditions of molten slags, thedimensions of slag are limited (ordinarily, about 800 mm at maximum),and it is difficult to provide large massive blocks of regular sizes. Onthe other hand, the size of blocks obtained by carbonation solidifyingthe slag and/or the rough grain like slag, can be arbitrarily adjustedby selecting shapes when carbonation-solidifying or selecting cut shapesafter the carbonation solidification, and it is possible to easilyobtain blocks of arbitrary sizes such as middle massive blocks or smallmassive blocks (broken blocks).

(4) It is preferable to use immersion blocks in rivers of optimumdensity.(specific gravity) in response to conditions of the river bottomor the water flowing speed. In this regard, the density of blocksobtained by carbonation solidifying the grain like slag and/or the roughgrain like slag having passed a metal removing treatment, can bearbitrarily adjusted by appropriately adjusting the bulk density(compaction density).

(5) In the case of blocks for sinking in the rivers obtained from thegrain like slag and/or rough grain like slag having passed the metalremoving treatment, since the main metal content is removed, if theblocks are applied in such river areas having problems concerning theshortage in oxygen of the river water or excessive supply of the ironcontent, there occurs no problem of the shortage in oxygen of the riverwater by oxidation of the metal or the excessive supply of the ironcontent by dissolution thereof. Further, the blocks for sinking in therivers obtained from slag having the metal removed have relatively muchcomponents attributing to the carbonation solidification of the slag byan amount of the metal removal, and those are useful for securingstrength.

(6) The blocks of the invention are ordinarily cut out from theconsolidated and piled mountain or charged layer, so that the block haverocky rugged forms, and when those are immersed or laid on the riverbed, they are easy to make large spaces between blocks or the river bedand the blocks in comparison with natural round blocks or similarnatural blocks seen at rivers, and so useful living and resting spacesfor water living creatures are easily formed.

Further, as mentioned above, the river immersion block of the inventionare very suited above all as artificially structural parts such as fishways or the artificial river beds (hereinafter, an explanation will bemade concerning a block for a fish way) in applications to the rivers,and in such applications, the blocks have the following merits.

(7) Surfaces of massive blocks obtained by carbonation-solidifying thegrain like slag and/or rough grain like slag are porous, and whensinking or laying them to the bottoms of the fish ways, water livingcreatures (for example, crusts or water living insects) which move bycatching with their claws the riverbed (surface projections as block orwater living plants) can easily move. In particular, the blocks of theinvention have porous and rugged surfaces, and also the pH as that of anatural block, and are ready for dissolving useful components, so thatwater living plants are easily adhere and live on the block surfaces, sothat water living creatures more easily move in the fish way.

(8) When using a stone for a fish way, it is sufficient to merely sinkthe massive blocks within the fish way, however preferably, the blocksmolded in a block or panel are fixedly laid on the bottom of the fishway. In this regard, since the blocks provided bycarbonation-solidifying the grain or rough grain like slag can bearbitrarily formed at production, block or panel shapes are easilyformed, and if employing such blocks, the construction is easy tofixedly and exactly lay the blocks on the bottom of the fish way.

(9) In comparison with a conventional foamed concrete, the constructionmay be carried out at low cost, the pH is lower than that of theconcrete, and it is desirable for water living creatures moving alongthe bottom of the fish way.

As the river immersion block of the invention is consolidated as thebinder of CaCO₃ or CaCO₃ and MgCO₃, it has sufficient strength, so thateven if a shock is affected while transferring or when sinking to lay ablock, cracks or destruction do not occur for a long period of year.

For providing suited compositions in response to places to be applied,it is possible to contain various kinds of additives (grain, rough grainor small massive additives) together with the grain like slag and/or therough grain like slag. As the additives, for example, enumerated aresuch as grains or rough grains to be a soluble silica source (solublesilica or soluble silica containing materials), grains or rough grainsto be an oxidized iron source (oxidized iron or oxidized iron containingmaterials).

The soluble silica or the iron source (iron or oxidized iron) containedin the immersion blocks in the rivers is dissolved in the water, therebyto usefully work to sustain the living of algae.

As grains or rough grains to be the soluble silica source, present arethe soluble silica and/or the material containing the soluble silica ofthe grain or rough grain. As the material containing the soluble silica,fly ash or clinker ash may be used which are generated by coalcombustion in such as a thermal power station. The fly ash containssoluble silica in an amount of 45 to 75 wt. %, while the clinker ashcontains 50 to 65 wt. %.

The water granulated slag from a blast furnace also contains relativelymuch soluble silica, and if parts or all of the slag are rendered to bethe water granulated slag, for example, if a slag from steel making andthe water granulated slag are mixed, a similar effect is brought aboutto the case of adding the additive to be the soluble silica source.

As the grain or the rough grain to be the oxidized iron source, presentare the grain like or rough grain like oxidized iron and/or the oxidizediron containing material, and in particular, cheaply available grain orrough grain are iron containing dusts generated in an iron-steel makingprocess. The iron containing dust is generally a dust from iron making,and ordinarily contains oxidized iron of around 75% in terms of Fe. Millscales also contain oxidized iron of around 70% in terms of Fe.

When obtaining blocks of relatively low specific gravity, it is usefulto use a water granulated slag of small specific gravity as at least onepart of the main raw material.

The river immersion block material of the present embodiment isrelatively porous, thereby bringing about the above mentioned effects(2). The percentage of voids is not especially limited, howevernormally, around 10 to 70% is a preferable percentage of voids.

Explanation will be made to a method of making block materials to beimmersed in rivers.

FIG. 10 is one example showing the production flow of the inventivemethod, and FIG. 11 is one example showing the production procedure. Theslag generated in the iron-steel making process is at first subjected tometal recovery to remove the main metal (grain iron). Ordinarily, sincethe slag content in slag and the metal are closely entangled, a metalrecovering treatment should be carried out on the grain or rough grainlike slag, and therefore, the slag is pulverized by such as a pulverizerto be mm-order or lower (for example, 5 mm or less), followed by a metalremoving treatment. The slag is sufficient with grain sizes enabling themetal removing treatment, and accordingly, if being relatively roughowing to properties of the slag, those enabling recovery of the metalare pulverized to a degree enabling to remove the metal.

There are some slags brought in as stated where the slags are naturallydestroyed to grain sizes enabling recovery of the metal, and thepulverizing treatment as mentioned above is not necessary therefor.

Ordinarily, the metal removing treatment is carried out by a magneticseparation of the magnetic separator (a method of removing the grainiron content from the slag by a magnet), however no limitation is madethereto. For example, available is a gravity density method such as anair separation making use of a difference in specific gravity betweenthe metal content and the slag content.

The metal content in the slag is removed by a metal removing treatment.

The grain like slag and/or the rough grain like slag having passed ametal removing treatment are added with the additives if required, andCaO or MgO necessary for carbonation reaction are short in the slag, onekind or more selected from CaO, Ca(OH)₂, MgO and Mg(OH)₂ are added asrequired and mixed with the slag. As the additives, for example, addedare such as grains or rough grains to be a soluble silica source(soluble silica or soluble silica containing materials), grains or roughgrains to be oxidized iron source (oxidized iron or oxidized ironcontaining materials) and CaO. Specific examples thereof are asmentioned above.

Mixture of the slag and the additive raw materials such as the additivesor CaO may depend on arbitrary methods, for example, a method of mixingthe addition raw material and the slag exhausted from a metal removingfacility in a hopper, a method of adding the addition raw material tothe slag having passed a metal removing treatment to mix in the metalremoving facility, a method of mixing by a heavy machinery as a shovel,or a method of mixing by a concrete mixer car (concrete agitator).

The slag, which has been added with the additives as needed and mixed,is piled for carbonation solidification or filled up in optional spaces.

Herein, for piling, an open-air freighting is sufficient, and it ispreferable to cover the piled mountains with sheets such that the blowncarbon dioxide flows allover the piled mountains, and for preventing theslag from scattering or fading by rainwater.

For piling or packing the slag, available are pits encircling threecorners with partitioning walls, molding frames or containers encirclingfour corners with the partitioning walls. When piling or packing theslag within the pit, it is preferable to cover the piled or filled-upmountains with the sheets similarly to the open-air freighting. Further,when using the molding frame or container, it is desirable to cover theslag packed bed with the sheet or provide a cover body. FIG. 11 shows astate where the packed bed A is formed within the frame.

The piling amount or the packing amount of the slag are not limited, andsaid amounts of several tons or several hundred tons are sufficient, orsaid amount corresponding to one piece of the block material or severalpieces are enough. Thus the amount is optional. Although the piling orfilling amount is much, if the piled mountain or the packed bed afterthe carbonation solidification are pulverized by the heavy machinery,massive block materials can be cut out, and such cut-out massive blockshave merits of irregular fractures for catching algae. From theviewpoint of productivity and function as river immersion blocks, it ispreferable that the slag piling or packing amounts are much to a certaindegree. Specifically, scales of 10 tons or more are desirable.

The bulk density (compaction density) of the slag pile or layer ispreferably adjusted in response to a density of block to be produced.Namely, the immersion block in rivers should be adjusted with respect tothe density in response to conditions of the river bottom or the waterflowing. Since the adherence of algae, the living degree thereof ordissolution of useful components from the interior of blocks are variedby the porosity (vacancy) of the block materials, it is often preferableto adjust the porosity of the blocks in response to conditions of therivers where the blocks are used.

The density of block to be produced by the method of the presentembodiment depends on the bulk density (compaction density) of the piledmountain or packed bed, and so, it is possible to adjust the tighteningdegree of the piled mountain or packed bed, and by adjusting the bulkdensity, the density of block can be easily adjusted.

The tightening degree of the slag piled mountain or packed bed isoptional, however ordinarily, the bulk specific gravity/true specificgravity ranges from 0.3 to 0.9, that is, the tightening is carried outto a degree that the vacancy within the piled mountain or packed bed is70 to 10%.

The tightening may depend on a method of tightening the upper part ofthe piled mountain or packed bed or a method of providing vibration totighten the piled mountain or packed bed. By adjusting the tighteningdegree, the density of the piled mountain or packed bed is adjusted.When producing blocks of low density, the tightening is not performed,and the carbonation solidification is practiced as piled or filled up.

As an actual tightening method, when tightening the piled mountain orpacked bed within the above mentioned pit or molding frame, weighinglines for showing a target volume are marked on the interior of the pit,a molding frame or container, and the slag whose weight is known is laidtherein, and the tightening is continued until the upper face of thepiled mountain or packed bed comes to the weighing line.

After completing the adjustment of the bulk specific gravity of thepiled mountain or packed bed of slag, the carbonation reaction occurs inthe piled mountain or packed bed under the existence of carbon dioxidefor carbonation-solidifying the slag. Specifically, carbon dioxide or acarbon dioxide containing gas is blown into the piled mountain or packedbed of slag, otherwise the piled mountain or packed bed is laid under anatmosphere of carbon dioxide or a carbon dioxide containing gas forcarrying out the carbonation solidification of slag.

The above blowing manner is not especially limited, however it is mosteffective to equip a gas blowing instrument at the bottom of the piledmountain or packed bed and blow the gas through this instrument.Actually, gas supplying pipes or hoses are disposed at an appropriatepitch (e.g., 300 mm to 400 mm) in the bottom of the mountain or layer(if using the pits, molding frames or containers, in beds thereof) forblowing the carbon dioxide or the carbon dioxide containing gas.

Further, as the manner for laying the mountain or layer in theatmosphere of the carbon dioxide or the carbon dioxide containing gas,the mountain or layer are laid in air-tight spaces (including thecontainer), into which the carbon dioxide or the carbon dioxidecontaining gas is supplied by an arbitrary embodiment.

As the carbon dioxide containing gas to be employed, suited are, forexample, an exhaust gas from a limestone baking plant (normally, CO₂:around 25%) or an exhaust gas from reheating furnace (normally, CO₂:around 6.5%) of an integrated steel making works. However no limitationis made thereto. If the concentration of carbon dioxide in the carbondioxide containing gas is too low, a problem occurs that the treatingefficiency is decreased, however no other problem appears. Thus, theconcentration of carbon dioxide is not limited, however for efficientlytreating, it is preferably 3% or higher.

The gas blowing amount of the carbon dioxide or the carbon dioxidecontaining gas is not limited, either, and as an ordinary standard, itis good to use a gas blowing amount of around 0.004 to 0.5 m³/min·t. Inaddition, there is no limitation especially required for the gas blowingtime (carbonation treating time), and as a standard, it is desirable toblow the gas until the blowing amount of carbon dioxide (CO₂) reaches 3%or more of the weight of the slag, that is, until carbon dioxide (CO₂)of 15 m³ or more per 1 ton of a material in terms of the gas amount issupplied.

The carbon dioxide or the carbon dioxide containing gas to be blown intothe piled mountain or packed bed of slag is sufficient at roomtemperature, and if the gas exceeds room temperature, this is better forreactivity. An upper limit of the gas temperature is a temperature fordecomposing CaCO₃ into CaO and CO₂ or MgCO₃ into MgO and CO₂, and whenusing gas at high temperature, gas at a temperature of not bringingabout such decompositions should be used.

For carbonation-solidifying the slag by utilizing the reaction of CaO,MgO and carbon dioxide, a water content is necessary, and it isdesirable to have around a 3 to 10% water content ratio in the slagimmediately before starting the carbonation treatment. This is becausethe carbonation reaction is accelerated by dissolving CaO, MgO andcarbon dioxide in the water. Therefore, if the water content in slag forcomposing the piled mountain or charged layer is too low, the water maybe added to the slag in the mixing course of FIG. 6 for adjusting thewater content for heightening the amount of water contained in slag. Ifthe carbon dioxide or the carbon dioxide containing gas is once blowninto the water to saturate H₂O, followed by blowing it into the piledmountain or packed bed, the slag is prevented from being dried toaccelerate the carbonation reaction.

Further, it is sufficient to adjust the water content in mixture to be avalue at which a compression strength of a massive substance is at amaximum after the carbonation treatment. This value of the water contentis obtained as follows.

(a) A raw slag of more than 3 standard is prepared, where water of anoptional amount of more than a water absorption rate of the raw slaggrain is added to 100 wt parts of the raw slag. The above mentionedwater absorption rate is that of a fine aggregate or a coarse aggregatespecified by JIS A1109 or A 1110.

(b) Respective raw slags are charged in the molding frames so that theporosity at drying is kept to be constant and homogenous, and thecharged layers are formed.

(c) The charged layer is blown with carbon dioxide gas humidified at 10to 40° C. at a determined amount for practicing carbonation curing for afixed time so as to solidify the raw slag.

(d) The compression strength of the solidified slag is measured forobtaining a maximum value thereof. The value of the water contentcorresponding to the maximum value is the optimum water content.

By supplying the carbon dioxide or the carbon dioxide containing gasinto the piled mountain or the charged layer of the slag, CaCO₃ or MgCO₃is produced by the reaction between CaO (or Ca(OH)₂) or MgO (or Mg(OH)₂)and the carbon dioxide. CaCO₃ or CaCO₃ and MgCO₃ are rendered to bebinders for solidifying the slag grain (if the additive is mixed, theslag grain and additive grain).

After completion of the carbonation solidification, the piled mountainor the charged layer are broken into required sizes by heavy machinery,and cut out into massive block materials to be immersed in the sea.Ordinarily, the blocks are cut out into sizes of 80 to 1500 mm. By thispulverization when cutting out, the blocks have fractures ofirregularities for easily catching such as algae.

In the method of the present embodiment, if the volume of charged layeris sufficiently small, it needs no cutting out. It can be utilized asthe block material as it is divided into two parts. For example, thiscase may be applied to production of the block or panel shaped blocks,and if dividing into two parts by pulverizing or breaking thecarbonation-solidified block blocks, two pieces of block like or panellike blocks having fractures on the surfaces may be produced.

The production method of the present invention has the following merits.

(1) Since the carbonation solidification is practiced under theconditions of piling the slag in a mountain or a charging layer, thedensity of the immersion block in rivers can be easily adjusted byadjusting the tightening degree of the piled mountain or the chargedlayer for adjusting the bulk specific gravity. As mentioned above, theblocks should be adjusted in the density or the porosity in response toconditions of the river bottom or water flowing, and as the productionmethod of the blocks it is a big merit that the adjustment can bearbitrarily and easily carried out. A conventionally known technique isto carbonation-solidify granulates, which is however difficult to adjustthe density of non-treated materials in wide ranges.

(2) The method of the present invention carries out the carbonationsolidification under the condition of piling or charging the slag in amountain or a layer, breaks the carbonation-solidified mountain or layerfor cutting out the massive blocks into desired sizes or utilizes thecharged layer as blocks as they are, or divides into massive blocks. So,by appropriately selecting sizes of the cut-out blocks or the chargedlayer, the blocks of optional sizes (for example, 80 to 1500 mm) can beobtained, and large massive blocks can be easily obtained. In the priorart of carbonation-solidifying granulated pellets, sizes of obtainedmassive products are 30 to 50 mm at the most, besides inevitablyproducing massive ones of a small size. Thus, as the production methodof river immersion blocks, it is a big advantage that large massiveblocks can be obtained.

(3) When fixedly laying blocks to artificially structural parts orartificial river beds of fish ways, the blocks to be employed aredesirably shaped in a block or a panel, and in the inventive method, byappropriately selecting sizes or shapes of the charged layer, suchshaped blocks can be easily produced.

(4) After the carbonation solidification, the piled mountain or thecharged layer of the slag are broken by heavy machinery, and cut outinto massive block materials, so that the blocks, which have surfaces(fractures) of irregularities for easily catching algae, can beobtained. Further, with respect to the block or panel shaped blocks ofthe above (3), if dividing into two parts by pulverizing or breaking thecarbonation-solidified blocks, two pieces of a block like or a panellike block having fractures on the surfaces may be produced.

EXAMPLE 5

A grain like converter slag of grain size being 3 mm or smaller, waspiled 1.5 m in a pit of 4 m width×6 m depth, and moderately tightened,then the pit was closed and blown with carbon dioxide 50 Nm³/hr for 3days so as to solidify the slag. The carbonation-solidified slag wasbroken by heavy machinery to produce the massive block materials havinga size of about 30 to 250 mm with enough strength as river immersionblocks.

EXAMPLE 6

The raw material was dephosphorized slag grain like of a diameter of 6mm or less being 100 wt. %, and blocks for fish ways were produced bythe following two methods.

(1) The grain like slag was charged in porous molding frames of 50 cm×50cm×15 cm, and tightened, and then 60 pieces of frames were set withinthe pit such that spaces were created between the frames. The pit wasclosed and blown with carbon dioxide of 70 Nm³/hr for 5 days forsolidifying the slag. After that, the molding frames were taken off, andthe block shaped blocks for fish ways were obtained.

(2) The grain like slag was charged in porous molding frames of 100cm×100 cm×50 cm. For charging, at intermediate positions of 100 cm widthof the molding frames, polyethylene made partitions opening at thecentral parts were interposed (100 cm×100 cm×2 mm, and opening: 85 cm×85cm). The grain like slab was charged, and the wholes were tightened. 18pieces of molding frames were set within the pit such that spaces werecreated between the frames. The pit was closed and blown with carbondioxide of 70 Nm³/hr for 5 days for solidifying the slag. After that,the molding frames were taken off, and the obtained block shaped blockswere broken into two pieces at the central parts interposing thepartitions, having fractures (broken faces) on the upper surfaces.

The block shaped blocks for fish ways produced by the above (1) and (2)were laid as embodied in FIG. 9A on the bottom of the fish wayconstructed with concrete. Incidentally, the blocks (2) for the fish waywere laid such that the fractures composed the bottom of the fish way.Thereby, differently from smooth bottom parts as the concrete (concreteblock or concrete construction), the obtained fish way had the porousand rugged rough bottom for shells easily moving.

As the inventive block of the invention is almost equal pH as thenatural block by neutralizing reaction at production, there is not sucha phenomenon that the concrete-made fish way heightens pH in the surfaceby elements dissolved at starting the use after construction, and algaeare delayed in adhering to. As the bottom of the fish way composed ofthe inventive blocks has the porous and rugged rough face, it wasconfirmed that algae adhered to the bottom and lived in a relativelyshort period.

As mentioned above, according to the above mentioned presentembodiments, neither a shortage in oxygen in the river water or anincrease of pH are encountered, and when sinking or laying as blocks forriver beds, the block materials can exhibit excellent performance informing living spaces for fishes or rearing of water living plants suchas algae, and in addition, those display special functions in the movingof other creatures than fishes or rearing of water living plants whensinking or laying them on artificially structural parts or artificialbeds provided at dams or barrages. Also it is possible to offer theblock materials for sinking in the rivers which are adjustable in sizeand density.

In particular, in the production method of the present invention, sincethe carbonation solidification is carried out under the conditions ofpiling or packing the slags, it is possible to produce a river immersionblock of optional density and size easily and at a low cost by adjustingthe degree of tightening of the piled mountain or the charged layer, orappropriately selecting sizes of the carbonation-solidified blocks to becut out. Especially, for the repairing of river beds, an enormous amountof blocks are required, however according to the present invention,blocks can be supplied at low cost, in comparison with cases of usingnatural blocks or concrete materials. Thus, the cost of construction canbe curtailed.

There are some slags which have a property to be floured by atransforming expansion of γ-dicalcium silicate generated when cooling,or expansion caused by hydration of free CaO. Conventionally, suchfloured slag has been difficult to use as materials, however in thepresent embodiments, a floured slag can be utilized as a raw material.Further, this is a very profitable invention also in a regard ofusefully using slags generated in the iron-steel making process.

Creating Method of Algae Places

The inventors noticed an increasing power or an increasing action ofmarine algae in existing algae planting places, and got an idea ofmaking use of existing algae planting places per se in adhering andliving of seeds and saplings of marine algae to bases. That is, theinventors had the idea of temporarily laying materials to be bases forcreating algae places so as to cause seeds and saplings to naturallyadhere and live on the surfaces of materials for utilizing thesematerials as bases for creating algae planting places. As a result ofhaving made experiments and studies based on this idea, they found thatif materials of blocks were laid in existing algae planting places,marine algae adhered and lived on the surfaces of materials in arelatively short period of day. Further, if materials with algae livingwere moved as seeding materials to places of creating algae plantingplaces, and at the same time new materials (marine algae not adhering)were placed around their circumferences, marine algae of seedingmaterials increased on the circumferential materials, and formed unitsof a community of algae comprising the algae planting places.

With respect to the materials to be bases for creating the algaeplanting places including the above seeding materials, suitableproperties of materials were investigated, and it was found that if amaterial had a weight of a degree not to be brought up by the seacurrent, however, enabling to stay on the sea bottom, the propertieswere of no problem, and preferable were such materials of surfaceproperties for easily catching spores or seeds of marine algae, namely,surfaces having ruggedness or projections. Above all, very suited asmaterials were artificially made blocks where slag generated in theiron-steel making process was made massive through a special technique,exhibiting excellent effects also in sustaining the living of marinealgae.

The present embodiment has the following characteristics.

A method of creating or improving algae planting places, characterizedby temporarily sinking materials comprising weighty substances onexisting algae planting places, adhering and rearing marine algae on thesurfaces of said materials, then recovering the materials for creatingalgae planting places or moving as seeding materials to places forincreasing marine algae, and disposing other materials around saidseeding materials for increasing marine algae of said seeding materialon said other materials.

As the above mentioned materials, it is preferable to employartificially made blocks as follows.

(a) An artificially made block of a main raw material being a slaggenerated in an iron-steel making process, where the slag isconsolidated with a binder of CaCO₃ produced by a carbonation reaction,and made massive. This slag is at least one selected from the groupconsisting of grain like slag, rough grain like slag and small massiveslag. The slag is sufficient with grain like slag or rough grain likeslag having passed a metal removing treatment.

(b) An artificially made block of a main raw material being a slaggenerated in an iron-steel making process, where the slag isconsolidated with a binder of CaCO₃ and MgCO₃ produced by a carbonationreaction, and made massive. The embodiment includes a case where MgCO₃exists as a hydrate, hydroxide salt or double salt. The slag is at leastone selected from the group consisting of grain like slag, rough grainlike slag and small massive slag. The slag is sufficient with grain likeor rough grain like slag having passed a metal removing treatment.

(c) An artificially made block of a main raw material being a slaggenerated in an iron-steel making process, grain like additives and/orrough grain additives, where a mixture of the slag and the additives isconsolidated with a binder of CaCO₃ produced by a carbonation reaction,and made massive. This slag is at least one selected from the groupconsisting of grain like slag, the rough grain like slag and smallmassive slag. The slag is sufficient with grain like or rough grain likeslag having passed a metal removing treatment.

(d) An artificially made block of a main raw material being a slaggenerated in an iron-steel making process, grain like additives and/orrough grain additives, where a mixture of the slag and the additives isconsolidated with a binder of CaCO₃ and MgCO₃ produced by a carbonationreaction, and made massive. The embodiment includes a case where MgCO₃exists as a hydrate, hydroxide salt or double salt. This slag is atleast one selected from the group consisting of grain like slag, roughgrain like slag and small massive slag. The slag is sufficient withgrain like or rough grain like slag having passed the metal removingtreatment.

Other than creating algae planting places in such lands where algae donot grow or are decayed, these embodied methods may be applied forimproving (rearing the algae) places where algae planting places aredecaying.

A detailed explanation will be made to a method of creating algaeplanting places (or improving method).

In the present embodiment, at first, materials to be seeding materialsare temporarily immersed in the existing algae places (in particularpreferably, natural algae places). As an existing algae place, first ofall, a natural algae place exists in circumstances where marine algaeare easy to increase (circumstances of light, water quality or oceancurrent governing growth of algae) in comparison with places where algaedo not naturally live, and besides the algae planting place is a sitewhere seeds or spores (zoospore) released from algae exist in thehighest density. Accordingly, an existing algae place is the site mostsuited for adhering and rearing algae on the surfaces of the materials.

The materials to be immersed to the algae planting places are of noproblem regarding material properties or shapes, if the materials have aweight of a degree not to be brought up by the ocean current, however,enabling to stay on the sea bottom. As the materials, if, for example,natural blocks, artificial blocks (including massive slag or concreteblocks), metallic materials (e.g., steel materials or cast products),plastic materials, or their compound materials, exceed a specificgravity being 1, no problem is involved with material properties.Further, shapes are not especially limited, and appropriate forms may beselected as massive, lengthy, block, plate, or one material in a basketor a net of plural massive substances.

Materials having ruggedness or indentations on the surfaces are easy foradhering spores seeds of marine algae, and rooting germs. When thematerial is a block, it is most desirable to form the rugged surfacewith a broken face when pulverizing. As the broken face of the blockmaterial is formed with countless ruggedness, the adhering of sporesseeds of marine algae and the living of germs are good.

Especially preferable are artificially made blocks which will bereferred to in detail.

In regard to materials other than one material which is made by packingplural massive substances in a basket or a net, when temporarily sinkingsaid materials, it is convenient to wrap them in nets for pulling up orattach pulling-up instruments (such as wire rope) for making laterrecovery easy.

As to a period of season for temporarily sinking materials to the algaeplanting places, it is desirable to select a period when marine algae inthe algae planting places actively release spores or seeds. On thesurfaces of the immersion blocks, algae usually adhere and grow inseveral months to around one year, and some of those fast growingdevelop to mature making spores or seeds, or grow up nearly it. Asmentioned above, existing algae plating places (especially natural algaeplaces) have the most actively increasing property of marine algae onthe material surfaces in the circumferential aspect and in regard ofclosely existing of spores and seeds, and so algae can be rooted on thematerial surfaces in a relatively short period of a month.

When algae adhere to and live on the surfaces, the materials are pulledup for recovery. The materials are transferred as keeping algae livingon the material surfaces to places for building algae planting places(or improving algae planting places), and are again immersed as seedingmaterials. At the same time, new materials (that is, other materials foradhering marine algae) are immersed around the seeding materials. Then,for example, the seeding materials are laid one to two pieces in a rangeof around 10 m×10 m, and new materials are disposed around them under arelatively close condition. Further, bases are built on which newmaterials are piled, and seeding materials are laid therein orincorporated in the bases. The inventive method includes such a case inthe embodiments of sinking new materials around seeding materials.

In general, places for creating algae planting sites are at a sea bottomof a depth of 20 m or lower, and the creating work may be carried out bya procedure of sinking to the sea bottom new materials conveyed by aship and not yet adhering marine algae for making bases, and thensuspending seeding materials.

Properties, tendencies or forms of new materials to be immersed aresimilar to those of materials to be the above-mentioned seedingmaterials. Different materials in properties, tendencies or forms may beemployed.

According to such method of creating the algae planting places, sporesor seeds released from algae of the seed materials adhere to theneighboring materials, grow ordinarily in a relatively short period ofaround one year, and form units of community. Therefore, materials to beadhered with algae are immersed allover places for planting algae, andamong them said seeding materials are dotted, whereby creation of algaeplanting places can be performed easily and in a short term, though belarge scaled places.

The method of this embodiment may be said to be a method of creatingalgae planting place provided with the advantages of the conventionalmethods and with further improved advantages. Namely, the inventivemethod makes use of an increasing action of marine algae in existingalgae planting places for adhering and rearing algae in materials to beseeding material for building algae planting places, and similarly tothe conventional methods of transplanting seeds and saplings tomaterials, the inventive method can exactly cause marine algae to rootmaterials, and can create algae planting places which exactly increasealgae in a relatively short term in comparison with the maintenance freemethod of creating algae planting places. In addition, the inventivemethod has a merit of widely selecting ranges for making algae plantingplaces.

Beside, the method of this embodiment which adheres and rears algae tomaterials in sites most suitable for germinating and growing in thecircumstances of algae planting places, so that algae living on thematerial surfaces are good in growing and rooting. Therefore, thepresent method is high in probability of surviving and living than theconventional method of transplanting seeds and saplings of marine algaeto materials, and has a big advantage of scarcely requiring growthmanagement after the transplanting.

On the other hand, the method of this embodiment is different from theconventional maintenance free method of creating algae planting placesonly in that materials to be seed materials are temporarily immersed fora certain period in the existing algae planting place, and are recoveredto be moved to places for creating algae planting sites, hardlyrequiring other artificial works or a growth management of the marinealgae. Thus, this method may be said to have simplicity and economics incost near to the conventional maintenance free method of creating algaeplanting places.

Further reference will be made to the suitable materials as those to beemployed in the method of the embodiments.

As the material (for the seeding material and for the base creatingalgae planting places), is an artificially made block of a main rawmaterial being a slag generated in an iron-steel making process, wherethe slag is consolidated with a binder of CaCO₃ or CaCO₃ and MgCO₃ isproduced by a carbonation reaction, and made massive. It is found thatsuch massive block for an algae planting place does not involve ashortage of oxygen or increase of pH, and displays excellent effectsalso in the rearing of marine algae.

Further, the artificially massive block can be easily produced by pilingor packing grain like or rough grain like slag in a desired density andcausing a carbonation reaction in the piled mountain or packed bed underthe existence of carbon dioxide, thereby solidifying grain like or roughgrain like slag. The block material produced by this method can beadjusted to the desired density and size in response to the conditionsof the sea bottom or ocean currents to be applied, and can be easilymade massive.

Specifically, the above-mentioned artificially made block has thefollowing advantages.

Since the main metal content (grain iron) is removed, the block does notinvolve a shortage of oxygen in the seawater owing to oxidation of theiron content.

Major parts of CaO (or Ca(OH)₂ produced from CaO) contained in the slagare changed into CaCO₃, it is possible to avoid an increase of pH in thesea water by CaO.

The massive slag obtained by carbonation-solidifying the grain like slagand/or the rough grain like slag, has porous properties as a whole(surface and interior), so that the marine algae easily attach to thesurfaces of blocks. Besides, since the interior of block is also porous,elements contained in blocks useful for the growing and accelerating ofthe algae (for example, soluble silica or oxidized iron content) areeasily dissolved in the seawater. Therefore, those can effectivelyaccelerate the growing of the marine algae in comparison with the caseof using massive slags per se for building sea-immersion blocks orconcrete products where the slag is an agglomerate.

In particular, in the method of this embodiment, it is necessary toeffectively accelerate the adherence and rearing of algae to thematerials temporarily immersed in the existing algae planting place, theincrease and living of algae on the materials disposed around theseeding materials, and above all to accelerate the living of young algaeon the block surfaces. In this regard, since useful elements dissolve inthe water from the immersion blocks, such effectively works ifindividuals of the marine algae are near thereto, and are very useful tosustain the living of young algae. Consequently, the useful elementsenable the young algae to promote to breed efficiently, and thisinvention can provide higher effectiveness.

When using massive slags per se as immersion blocks for algae plantingplaces, because of restraints of cooling methods or conditions of moltenslags, dimensions of the slag are limited (ordinarily, about 800 mm atmaximum), and it is difficult to provide large massive blocks of regularsizes. On the other hand, the size of blocks obtained by carbonationsolidifying grain like slag and/or rough grain like slag, can bearbitrarily adjusted by selecting shapes during carbonation-solidifyingor by selecting cut shapes after the carbonation solidification, and itis possible to easily obtain large massive blocks particularly suited toalgae planting places.

It is preferable to use immersion blocks in the sea of an optimumdensity (specific gravity) in response to conditions of the sea bottomor ocean currents. For example, when sinking blocks of a large densityto sea bottoms such as a piling of sludge, the blocks are immersed intothe sludge and cannot serve as bases of algae places. In this regard,the density of blocks obtained by carbonation solidifying grain likeslag or rough grain like slag having passed a metal removing treatment,can be arbitrarily adjusted by appropriately adjusting the bulk density(compaction density) of the slag during carbonation solidifying.

As the slags to be main raw materials of the above mentionedartificially made blocks, there may be enumerated slags from blastfurnaces such as a slowly cooled slag or a water granulated slagtherefrom; slags from an iron-steel making process such asdephosphorized slag, desulfurized slag desiliconized slag, decarburizedslag or casting slag generated in a pre-treatment, a converter orcasting; slags from iron ore reduction; or slags from electric furnaces.However, no limit is provided on them. Slags mixed with two kinds ormore of slag may be used.

In general, the slag generated in an iron-steel making process contains,a considerable amount of CaO (ordinarily, 20 wt % to 60 wt %). Theartificial block is produced by changing CaO or Ca(OH)₂ changed from CaOcontained in grain like slag and/or rough grain like slag (including CaOand Ca(OH)₂ as needed) into CaCO₃ by the above mentioned carbonationreaction, consolidating the slag grain (when including the additives,grains of additives and slag) with a binder of CaCO₃, and making itmassive.

The major parts of the slag contain a certain amount of MgO togetherwith CaO. An artificial block where such slag is the raw material isproduced by changing MgO or Mg(OH)₂ changed from MgO (including MgO andMg(OH)₂ as needed) into MgCO₃ by the above mentioned carbonationreaction, consolidating the slag grain (when including the additives,grains of additives and slag) with a binder of MgCO₃ and CaCO₃, andmaking it massive.

Since an artificial block is made by closely consolidating CaCO₃ orCaCO₃ and MgCO₃ produced by a carbonation reaction of the slag of asmall grain size, the strength is sufficient, and even if a shock isaffected during transportation or when sinking it in the sea, whilebeing laid in the sea bottom for a long period, there is almost nopossibility that a crack or destruction will occur.

An artificial block may contain various kinds of additives (grain likeor rough grain like additives) together with the grain like or roughgrain like slag for providing suitable compositions in response toconditions of sea areas to be applied therewith. As the additives,enumerated are, for example, grain or rough grain (soluble silica,soluble silica containing material) to be a soluble silica source, grainor rough grain (oxidized iron, oxidized iron containing material) to bean oxidized iron source, or CaO of grain or rough grain. For containingCaO as the additive in the artificial block, it is necessary to leaveCaO contained in slag or at least one part of CaO to be significantlycontained in slag remaining as non-reacted CaO after the carbonationreaction.

The soluble silica or the oxidized iron contained in the artificialblock is dissolved in the sea to usefully work to sustain the living ofmarine algae. If phosphorus is a cause of red tide or sulfur is a causeof blue tide are substantially contained in the sea bottom, CaOcontained a bit in the sea immersion block absorbs these phosphorus orsulfur. As mentioned above, there is a problem of increasing the pH inthe sea water if CaO is substantially contained in the block, howeverCaO is sufficient with a small amount of a degree remaining after thecarbonation solidification for absorbing phosphorus or sulfur.

As grains or rough grains to be the soluble silica source, included arethe soluble silica and/or the material containing the soluble silica ofthe grain or rough grain. As a material containing the soluble silica,fly ash or clinker ash may be used which are generated by coalcombustion in such as a thermal power station. The fly ash containssoluble silica in an amount of 45 to-75 wt %, while the clinker ashcontains 50 to 65-wt %.

The water granulated slag from a blast furnace also contains relativelymuch soluble silica, and if parts or all of the slag are rendered to bethe water granulated slag, for example, if a slag by a steel making andthe water granulated slag are mixed, a similar effect is brought aboutto the case of adding the additive to be a soluble silica source.

As the grain or the rough grain to be the oxidized iron source, includedare grain like or rough grain like oxidized iron and/or an oxidized ironcontaining material, and in particular, cheaply available grain or roughgrain are iron containing dusts generated in an iron-steel makingprocess. The iron containing dust is generally a dust from iron making,and ordinarily contain oxidized iron of around 75% in terms of Fe. Millscales also contain oxidized iron of around 70% in terms of Fe.

As mentioned above, when sinking blocks of a large specific gravity tothe sea bottom such as a piling of sludge, the blocks are immersed intothe sludge and cannot serve as algae places or fish gathering places.Therefore, with respect to the block material to be used for the seabottom of piled sludge, it is preferable that a slag of relatively smallspecific gravity is a main raw material, and specifically, it is usefulto use water granulated slag of a small specific gravity than that ofother slag as at least one part of the main raw material.

The artificial block material is relatively porous, thereby bringingabout the above mentioned effects. The percentage of voids is notespecially limited, however normally, around 10 to 70% is a preferablepercentage of voids.

The artificial block is produced through the same method as making thesea immersion block explained referring to FIGS. 5 to 8.

EXAMPLE 7

A mortar was poured into a molding frame of 1.5 m×1.5 m×1.5 m, and thesolidified concrete block was divided into two by a breaker (rock drill)to produce blocks having fractured faces for the algae planting placefor adherence.

One of the above blocks was transported to the sea of a natural algaeplanting place, put in a pulling-up net, and was temporarily laid in thealgae planting place, turning upward the fractured face. A period of theseasons for sinking blocks was selected 9 months just before spendingspores from the natural marine algae planting place in order thatsedimentary substances did not cover the block surfaces before sporesadhered thereto. After about one year, it could be confirmed that algaelived and rooted on the blocks surface, and the block was pulled up andtransported to the algae planting place as the seeding material.

As the algae planting place, taking the water quality and the oceancurrent into consideration, a sea bottom of 4 m deep enough, separatedfrom the existing algae place, was selected. In this place, 20 pieces ofnew blocks without adhering algae were immersed in the range of about 10m diameter, turning the fractured faces upward, and at the centerthereof, the above mentioned seeding materials were again immersed.

After about one year, when this algae planting place was surveyed, itwas confirmed that all the blocks around the seeding blocks increasedthe fully living marine algae. The crop estimate by unit acreagesampling was carried out, and it was found that the marine algae of 521g/m² in humid weight lived.

EXAMPLE 8

A converter slag grain like of a grain size of 3 mm or less, was piled1.5 m in a pit of 4 m width×6 m depth, and moderately tightened, thenthe pit was closed and blown with carbon dioxide 50 Nm³/hr for 3 days soas to solidify the slag. The carbonation-solidified slag was broken byheavy machinery to produce 15 pieces of the massive block materialshaving a size of about 1.0 m to 1.5 m for the seeding materials and thebases of the algae planting place.

One of the above blocks was transported to the sea of a natural algaeplanting place similar to that of the above mentioned EXAMPLE 3, put ina pulling-up net, and was temporarily laid in the algae planting place,turning upward the fractured face. A period of the seasons for sinkingblocks was selected 9 months just before spending spores from thenatural marine algae planting place in order that sedimentary substancesdid not cover the block surfaces before spores adhering thereto.

After about one year, it could be confirmed that algae lived and rootedon the block surface, and the block was pulled up and transported to thealgae planting place as the seeding material.

As the algae planting place, the similar sea area and depth as theEXAMPLE 3 were selected. In this place, 14 pieces of new blocks withoutadhering algae were immersed in the range of about 10 m diameter,turning the fractured faces upward, and at the center thereof, the abovementioned seeding materials were again immersed.

After about one year, when this algae planting place was surveyed, itwas confirmed that all the blocks around the seeding blocks increasedthe fully living marine algae. The crop estimate by unit acreagesampling was carried out, and it was found that the marine algae of 689g/m² in humid weight lived.

According to the method of the invention, it is possible to select widealgae planting places, exactly create the algae places with less troubleand low cost, and to make algae places of a large scale.

Industrial Applicability

According to the method of the invention, it is possible to efficientlyabsorb and remove on an industrial scale CO₂ of exhaust gas from such asan industrial process by using only an agglomerate of solid particles asslag or concrete which is easily available and of low cost. Assuming touse as a CO₂ absorbing agent (an agglomerate of solid particles) onlysteel making slag from the iron-steel slag generated in the iron makingfirms all over Japan, and assuming to apply the inventive method toexhaust gas generated in the iron making firms all over Japan, it ispossible to curtail 1% of the amount of CO₂ generated it may be saidthat this reducing amount of CO₂ corresponds to 10% of the target valueof the above mentioned “a 10% reduction in comparison with 1990 of theenergy consumption in the production process” of the self-imposedbehavioral plan in the iron and steel business world, and corresponds to24% in comparison with 1995. Thus, in this sense, this is a veryepoch-making invention.

Further, not only in the reduction of CO₂ for industrial processes, butalso by the method of the invention, it is possible to select wide algaeplanting places, exactly create the algae places with less trouble andat low cost, and to make algae places of a large scale.

1. A method for reducing an exhaust carbon dioxide comprising: preparingagglomerates of solid particles containing at least one compoundselected from the group consisting of CaO and Ca(OH)₂; contacting anexhaust gas containing CO₂ with the agglomerates of the solid particlesin a reaction chamber, the solid particles having a film of adhesivewater on a surface of the solid particles; and fixing CO₂ in the exhaustgas as CaCO₃ in the solid particles to reduce CO₂ in the exhaust gas. 2.The method according to claim 1, wherein the agglomerates of the solidparticles are obtained by pulverizing materials containing CaO and/orCa(OH)₂ into grain and/or rough grain.
 3. The method according to claim1, wherein the step of contacting the exhaust gas comprises contactingan exhaust gas containing CO₂ with the agglomerates of the solidparticles by blowing the exhaust gas into the agglomerates of the solidparticles.
 4. The method according to claim 3, wherein the exhaust gascontaining CO₂ is blown into the agglomerates of the solid particlesfrom one direction.
 5. The method according to claim 1, wherein thewater content in the agglomerates of the solid particles is from 3 wt. %to 20 wt. %.
 6. The method according to claim 1, wherein a grain size ofthe solid particles is substantially 5 mm or less.
 7. The methodaccording to claim 1, wherein the exhaust gas introduced into thereaction chamber is at a temperature corresponding to the boiling pointof water or lower, within the reaction chamber.
 8. The method accordingto claim 1, wherein the reaction chamber is at a temperaturecorresponding to the boiling point of water or lower.
 9. The methodaccording to claim 1, wherein a temperature of the agglomerates of thesolid particles is at a temperature corresponding to the boiling pointof water or lower, within the reaction chamber.
 10. The method accordingto claim 1, wherein the step of contacting the exhaust gas containingCO₂ with the agglomerates of the solid particles comprises contacting apressurized exhaust gas with the agglomerates of the solid particles.11. The method according to claim 1, further comprising saturating H₂Oin the exhaust gas, prior to contacting the exhaust gas with theagglomerates of the solid particles.
 12. The method according to claim1, wherein the water content in the agglomerates of the solid particlesis a range of from 3 to 20 wt. %, and the exhaust gas is blown into theagglomerates of the solid particles, to contact the exhaust gas with theagglomerates of the solid particles.
 13. The method according to claim12, wherein the exhaust gas introduced into the reaction chamber is at atemperature corresponding to the boiling point of water or lower, withinthe reaction chamber, the reaction chamber is at a temperaturecorresponding to the boiling point of water or lower, and theagglomerates of the solid particles to be contacted with the exhaust gasis at a temperature corresponding to the boiling point of water orlower, within the reaction chamber.
 14. The method according to claim13, further comprising saturating H₂O in the exhaust gas prior tocontacting the exhaust gas with the agglomerates of the solid particles.15. The method according to claim 1, wherein the agglomerates of thesolid particles are at least one material selected from the groupconsisting of a slag generated in an iron and steel making process and aconcrete.
 16. The method according to claim 1, wherein the solidparticles of the agglomerates are at least one material selected fromthe group consisting of a slag generated in an iron and steel makingprocess and a concrete.
 17. The method according to claim 1, wherein theagglomerates of the solid particles are at least one material selectedfrom the group consisting of a slag generated in an iron-steel makingprocess, a concrete, a mortar, a glass, an alumna cement and a CaOcontaining refractory.
 18. A method of creating a seaweed bedcomprising: temporarily immersing a heavy material in an existingseaweed bed so that marine algae adhere and grow on a surface of thematerial; recovering the heavy material and transporting the heavymaterial as a seed material in a place for creating the seaweed bed; andarranging an adhering material for adhering the marine algae around theseed material so that the marine algae on the seed material isproliferated onto another seed material.